From 11451693e4081d32ef65147c6ca08cd0094ae252 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:06 -0700
Subject: tty: n_gsm: fix missing mux reset on config change at responder

Currently, only the initiator resets the mux protocol if the user requests
new parameters that are incompatible to those of the current connection.
The responder also needs to reset the multiplexer if the new parameter set
requires this. Otherwise, we end up with an inconsistent parameter set
between initiator and responder.
Revert the old behavior to inform the peer upon an incompatible parameter
set change from the user on the responder side by re-establishing the mux
protocol in such case.

Fixes: 509067bbd264 ("tty: n_gsm: Delete gsm_disconnect when config requester")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-1-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index fa92f727fdf8..3d28ecebd473 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2373,7 +2373,7 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
 	 * configuration
 	 */
 
-	if (gsm->initiator && (need_close || need_restart)) {
+	if (need_close || need_restart) {
 		int ret;
 
 		ret = gsm_disconnect(gsm);
-- 
cgit v1.2.3


From aa371e96f05dcb36a88298f5cb70aa7234d5e8b8 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:07 -0700
Subject: tty: n_gsm: fix restart handling via CLD command

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapter 5.8.2 states that both sides will revert to
the non-multiplexed mode via a close-down message (CLD). The usual program
flow is as following:
- start multiplex mode by sending AT+CMUX to the mobile
- establish the control channel (DLCI 0)
- establish user channels (DLCI >0)
- terminate user channels
- send close-down message (CLD)
- revert to AT protocol (i.e. leave multiplexed mode)

The AT protocol is out of scope of the n_gsm driver. However,
gsm_disconnect() sends CLD if gsm_config() detects that the requested
parameters require the mux protocol to restart. The next immediate action
is to start the mux protocol by opening DLCI 0 again. Any responder side
which handles CLD commands correctly forces us to fail at this point
because AT+CMUX needs to be sent to the mobile to start the mux again.
Therefore, remove the CLD command in this phase and keep both sides in
multiplexed mode.
Remove the gsm_disconnect() function as it become unnecessary and merge the
remaining parts into gsm_cleanup_mux() to handle the termination order and
locking correctly.

Fixes: 71e077915396 ("tty: n_gsm: do not send/receive in ldisc close path")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-2-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 68 ++++++++++++++++-------------------------------------
 1 file changed, 20 insertions(+), 48 deletions(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 3d28ecebd473..daaffcfadaae 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2106,49 +2106,35 @@ static void gsm_error(struct gsm_mux *gsm)
 	gsm->io_error++;
 }
 
-static int gsm_disconnect(struct gsm_mux *gsm)
-{
-	struct gsm_dlci *dlci = gsm->dlci[0];
-	struct gsm_control *gc;
-
-	if (!dlci)
-		return 0;
-
-	/* In theory disconnecting DLCI 0 is sufficient but for some
-	   modems this is apparently not the case. */
-	gc = gsm_control_send(gsm, CMD_CLD, NULL, 0);
-	if (gc)
-		gsm_control_wait(gsm, gc);
-
-	del_timer_sync(&gsm->t2_timer);
-	/* Now we are sure T2 has stopped */
-
-	gsm_dlci_begin_close(dlci);
-	wait_event_interruptible(gsm->event,
-				dlci->state == DLCI_CLOSED);
-
-	if (signal_pending(current))
-		return -EINTR;
-
-	return 0;
-}
-
 /**
  *	gsm_cleanup_mux		-	generic GSM protocol cleanup
  *	@gsm: our mux
+ *	@disc: disconnect link?
  *
  *	Clean up the bits of the mux which are the same for all framing
  *	protocols. Remove the mux from the mux table, stop all the timers
  *	and then shut down each device hanging up the channels as we go.
  */
 
-static void gsm_cleanup_mux(struct gsm_mux *gsm)
+static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 {
 	int i;
 	struct gsm_dlci *dlci = gsm->dlci[0];
 	struct gsm_msg *txq, *ntxq;
 
 	gsm->dead = true;
+	mutex_lock(&gsm->mutex);
+
+	if (dlci) {
+		if (disc && dlci->state != DLCI_CLOSED) {
+			gsm_dlci_begin_close(dlci);
+			wait_event(gsm->event, dlci->state == DLCI_CLOSED);
+		}
+		dlci->dead = true;
+	}
+
+	/* Finish outstanding timers, making sure they are done */
+	del_timer_sync(&gsm->t2_timer);
 
 	spin_lock(&gsm_mux_lock);
 	for (i = 0; i < MAX_MUX; i++) {
@@ -2162,13 +2148,7 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm)
 	if (i == MAX_MUX)
 		return;
 
-	del_timer_sync(&gsm->t2_timer);
-	/* Now we are sure T2 has stopped */
-	if (dlci)
-		dlci->dead = true;
-
 	/* Free up any link layer users */
-	mutex_lock(&gsm->mutex);
 	for (i = 0; i < NUM_DLCI; i++)
 		if (gsm->dlci[i])
 			gsm_dlci_release(gsm->dlci[i]);
@@ -2370,19 +2350,11 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
 
 	/*
 	 * Close down what is needed, restart and initiate the new
-	 * configuration
+	 * configuration. On the first time there is no DLCI[0]
+	 * and closing or cleaning up is not necessary.
 	 */
-
-	if (need_close || need_restart) {
-		int ret;
-
-		ret = gsm_disconnect(gsm);
-
-		if (ret)
-			return ret;
-	}
-	if (need_restart)
-		gsm_cleanup_mux(gsm);
+	if (need_close || need_restart)
+		gsm_cleanup_mux(gsm, true);
 
 	gsm->initiator = c->initiator;
 	gsm->mru = c->mru;
@@ -2494,7 +2466,7 @@ static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 		for (i = 1; i < NUM_DLCI; i++)
 			tty_unregister_device(gsm_tty_driver, base + i);
 	}
-	gsm_cleanup_mux(gsm);
+	gsm_cleanup_mux(gsm, false);
 	tty_kref_put(gsm->tty);
 	gsm->tty = NULL;
 }
@@ -2597,7 +2569,7 @@ static int gsmld_open(struct tty_struct *tty)
 
 	ret = gsmld_attach_gsm(tty, gsm);
 	if (ret != 0) {
-		gsm_cleanup_mux(gsm);
+		gsm_cleanup_mux(gsm, false);
 		mux_put(gsm);
 	}
 	return ret;
-- 
cgit v1.2.3


From 1ec92e9742774bf42614fceea3bf6b50c9409225 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:08 -0700
Subject: tty: n_gsm: fix decoupled mux resource

The active mux instances are managed in the gsm_mux array and via mux_get()
and mux_put() functions separately. This gives a very loose coupling
between the actual instance and the gsm_mux array which manages it. It also
results in unnecessary lockings which makes it prone to failures. And it
creates a race condition if more than the maximum number of mux instances
are requested while the user changes the parameters of an active instance.
The user may loose ownership of the current mux instance in this case.
Fix this by moving the gsm_mux array handling to the mux allocation and
deallocation functions.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-3-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 63 ++++++++++++++++++++++++++++++++---------------------
 1 file changed, 38 insertions(+), 25 deletions(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index daaffcfadaae..f546dfe03d29 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2136,18 +2136,6 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 	/* Finish outstanding timers, making sure they are done */
 	del_timer_sync(&gsm->t2_timer);
 
-	spin_lock(&gsm_mux_lock);
-	for (i = 0; i < MAX_MUX; i++) {
-		if (gsm_mux[i] == gsm) {
-			gsm_mux[i] = NULL;
-			break;
-		}
-	}
-	spin_unlock(&gsm_mux_lock);
-	/* open failed before registering => nothing to do */
-	if (i == MAX_MUX)
-		return;
-
 	/* Free up any link layer users */
 	for (i = 0; i < NUM_DLCI; i++)
 		if (gsm->dlci[i])
@@ -2171,7 +2159,6 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 static int gsm_activate_mux(struct gsm_mux *gsm)
 {
 	struct gsm_dlci *dlci;
-	int i = 0;
 
 	timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
 	init_waitqueue_head(&gsm->event);
@@ -2183,18 +2170,6 @@ static int gsm_activate_mux(struct gsm_mux *gsm)
 	else
 		gsm->receive = gsm1_receive;
 
-	spin_lock(&gsm_mux_lock);
-	for (i = 0; i < MAX_MUX; i++) {
-		if (gsm_mux[i] == NULL) {
-			gsm->num = i;
-			gsm_mux[i] = gsm;
-			break;
-		}
-	}
-	spin_unlock(&gsm_mux_lock);
-	if (i == MAX_MUX)
-		return -EBUSY;
-
 	dlci = gsm_dlci_alloc(gsm, 0);
 	if (dlci == NULL)
 		return -ENOMEM;
@@ -2210,6 +2185,15 @@ static int gsm_activate_mux(struct gsm_mux *gsm)
  */
 static void gsm_free_mux(struct gsm_mux *gsm)
 {
+	int i;
+
+	for (i = 0; i < MAX_MUX; i++) {
+		if (gsm == gsm_mux[i]) {
+			gsm_mux[i] = NULL;
+			break;
+		}
+	}
+	mutex_destroy(&gsm->mutex);
 	kfree(gsm->txframe);
 	kfree(gsm->buf);
 	kfree(gsm);
@@ -2229,12 +2213,20 @@ static void gsm_free_muxr(struct kref *ref)
 
 static inline void mux_get(struct gsm_mux *gsm)
 {
+	unsigned long flags;
+
+	spin_lock_irqsave(&gsm_mux_lock, flags);
 	kref_get(&gsm->ref);
+	spin_unlock_irqrestore(&gsm_mux_lock, flags);
 }
 
 static inline void mux_put(struct gsm_mux *gsm)
 {
+	unsigned long flags;
+
+	spin_lock_irqsave(&gsm_mux_lock, flags);
 	kref_put(&gsm->ref, gsm_free_muxr);
+	spin_unlock_irqrestore(&gsm_mux_lock, flags);
 }
 
 static inline unsigned int mux_num_to_base(struct gsm_mux *gsm)
@@ -2255,6 +2247,7 @@ static inline unsigned int mux_line_to_num(unsigned int line)
 
 static struct gsm_mux *gsm_alloc_mux(void)
 {
+	int i;
 	struct gsm_mux *gsm = kzalloc(sizeof(struct gsm_mux), GFP_KERNEL);
 	if (gsm == NULL)
 		return NULL;
@@ -2284,6 +2277,26 @@ static struct gsm_mux *gsm_alloc_mux(void)
 	gsm->mtu = 64;
 	gsm->dead = true;	/* Avoid early tty opens */
 
+	/* Store the instance to the mux array or abort if no space is
+	 * available.
+	 */
+	spin_lock(&gsm_mux_lock);
+	for (i = 0; i < MAX_MUX; i++) {
+		if (!gsm_mux[i]) {
+			gsm_mux[i] = gsm;
+			gsm->num = i;
+			break;
+		}
+	}
+	spin_unlock(&gsm_mux_lock);
+	if (i == MAX_MUX) {
+		mutex_destroy(&gsm->mutex);
+		kfree(gsm->txframe);
+		kfree(gsm->buf);
+		kfree(gsm);
+		return NULL;
+	}
+
 	return gsm;
 }
 
-- 
cgit v1.2.3


From 284260f278b706364fb4c88a7b56ba5298d5973c Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:09 -0700
Subject: tty: n_gsm: fix mux cleanup after unregister tty device

Internally, we manage the alive state of the mux channels and mux itself
with the field member 'dead'. This makes it possible to notify the user
if the accessed underlying link is already gone. On the other hand,
however, removing the virtual ttys before terminating the channels may
result in peer messages being received without any internal target. Move
the mux cleanup procedure from gsmld_detach_gsm() to gsmld_close() to fix
this by keeping the virtual ttys open until the mux has been cleaned up.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-4-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index f546dfe03d29..de97a3810731 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2479,7 +2479,6 @@ static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 		for (i = 1; i < NUM_DLCI; i++)
 			tty_unregister_device(gsm_tty_driver, base + i);
 	}
-	gsm_cleanup_mux(gsm, false);
 	tty_kref_put(gsm->tty);
 	gsm->tty = NULL;
 }
@@ -2544,6 +2543,12 @@ static void gsmld_close(struct tty_struct *tty)
 {
 	struct gsm_mux *gsm = tty->disc_data;
 
+	/* The ldisc locks and closes the port before calling our close. This
+	 * means we have no way to do a proper disconnect. We will not bother
+	 * to do one.
+	 */
+	gsm_cleanup_mux(gsm, false);
+
 	gsmld_detach_gsm(tty, gsm);
 
 	gsmld_flush_buffer(tty);
-- 
cgit v1.2.3


From 06d5afd4d640eea67f5623e76cd5fc03359b7f3c Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:10 -0700
Subject: tty: n_gsm: fix wrong signal octet encoding in convergence layer type
 2

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapter 5.5.2 describes that the signal octet in
convergence layer type 2 can be either one or two bytes. The length is
encoded in the EA bit. This is set 1 for the last byte in the sequence.
gsmtty_modem_update() handles this correctly but gsm_dlci_data_output()
fails to set EA to 1. There is no case in which we encode two signal octets
as there is no case in which we send out a break signal.
Therefore, always set the EA bit to 1 for the signal octet to fix this.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-5-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index de97a3810731..3ba2505908e3 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -832,7 +832,7 @@ static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
 			break;
 		case 2:	/* Unstructed with modem bits.
 		Always one byte as we never send inline break data */
-			*dp++ = gsm_encode_modem(dlci);
+			*dp++ = (gsm_encode_modem(dlci) << 1) | EA;
 			break;
 		}
 		WARN_ON(kfifo_out_locked(&dlci->fifo, dp , len, &dlci->lock) != len);
-- 
cgit v1.2.3


From 7a0e4b1733b635026a87c023f6d703faf0095e39 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:11 -0700
Subject: tty: n_gsm: fix frame reception handling

The frame checksum (FCS) is currently handled in gsm_queue() after
reception of a frame. However, this breaks layering. A workaround with
'received_fcs' was implemented so far.
Furthermore, frames are handled as such even if no end flag was received.
Move FCS calculation from gsm_queue() to gsm0_receive() and gsm1_receive().
Also delay gsm_queue() call there until a full frame was received to fix
both points.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-6-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 53 ++++++++++++++++++++++++++++++-----------------------
 1 file changed, 30 insertions(+), 23 deletions(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 3ba2505908e3..4ce18b42c37a 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -219,7 +219,6 @@ struct gsm_mux {
 	int encoding;
 	u8 control;
 	u8 fcs;
-	u8 received_fcs;
 	u8 *txframe;			/* TX framing buffer */
 
 	/* Method for the receiver side */
@@ -1794,18 +1793,7 @@ static void gsm_queue(struct gsm_mux *gsm)
 	u8 cr;
 	int address;
 	int i, j, k, address_tmp;
-	/* We have to sneak a look at the packet body to do the FCS.
-	   A somewhat layering violation in the spec */
 
-	if ((gsm->control & ~PF) == UI)
-		gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf, gsm->len);
-	if (gsm->encoding == 0) {
-		/* WARNING: gsm->received_fcs is used for
-		gsm->encoding = 0 only.
-		In this case it contain the last piece of data
-		required to generate final CRC */
-		gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs);
-	}
 	if (gsm->fcs != GOOD_FCS) {
 		gsm->bad_fcs++;
 		if (debug & 4)
@@ -1993,19 +1981,25 @@ static void gsm0_receive(struct gsm_mux *gsm, unsigned char c)
 		break;
 	case GSM_DATA:		/* Data */
 		gsm->buf[gsm->count++] = c;
-		if (gsm->count == gsm->len)
+		if (gsm->count == gsm->len) {
+			/* Calculate final FCS for UI frames over all data */
+			if ((gsm->control & ~PF) != UIH) {
+				gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf,
+							     gsm->count);
+			}
 			gsm->state = GSM_FCS;
+		}
 		break;
 	case GSM_FCS:		/* FCS follows the packet */
-		gsm->received_fcs = c;
-		gsm_queue(gsm);
+		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
 		gsm->state = GSM_SSOF;
 		break;
 	case GSM_SSOF:
-		if (c == GSM0_SOF) {
-			gsm->state = GSM_SEARCH;
-			break;
-		}
+		gsm->state = GSM_SEARCH;
+		if (c == GSM0_SOF)
+			gsm_queue(gsm);
+		else
+			gsm->bad_size++;
 		break;
 	default:
 		pr_debug("%s: unhandled state: %d\n", __func__, gsm->state);
@@ -2024,11 +2018,24 @@ static void gsm0_receive(struct gsm_mux *gsm, unsigned char c)
 static void gsm1_receive(struct gsm_mux *gsm, unsigned char c)
 {
 	if (c == GSM1_SOF) {
-		/* EOF is only valid in frame if we have got to the data state
-		   and received at least one byte (the FCS) */
-		if (gsm->state == GSM_DATA && gsm->count) {
-			/* Extract the FCS */
+		/* EOF is only valid in frame if we have got to the data state */
+		if (gsm->state == GSM_DATA) {
+			if (gsm->count < 1) {
+				/* Missing FSC */
+				gsm->malformed++;
+				gsm->state = GSM_START;
+				return;
+			}
+			/* Remove the FCS from data */
 			gsm->count--;
+			if ((gsm->control & ~PF) != UIH) {
+				/* Calculate final FCS for UI frames over all
+				 * data but FCS
+				 */
+				gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf,
+							     gsm->count);
+			}
+			/* Add the FCS itself to test against GOOD_FCS */
 			gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->buf[gsm->count]);
 			gsm->len = gsm->count;
 			gsm_queue(gsm);
-- 
cgit v1.2.3


From a24b4b2f660b7ddf3f484b37600bba382cb28a9d Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:12 -0700
Subject: tty: n_gsm: fix malformed counter for out of frame data

The gsm_mux field 'malformed' represents the number of malformed frames
received. However, gsm1_receive() also increases this counter for any out
of frame byte.
Fix this by ignoring out of frame data for the malformed counter.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-7-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 4ce18b42c37a..2e3da8a4697e 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2044,7 +2044,8 @@ static void gsm1_receive(struct gsm_mux *gsm, unsigned char c)
 		}
 		/* Any partial frame was a runt so go back to start */
 		if (gsm->state != GSM_START) {
-			gsm->malformed++;
+			if (gsm->state != GSM_SEARCH)
+				gsm->malformed++;
 			gsm->state = GSM_START;
 		}
 		/* A SOF in GSM_START means we are still reading idling or
-- 
cgit v1.2.3


From 535bf600de75a859698892ee873521a48d289ec1 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:13 -0700
Subject: tty: n_gsm: fix insufficient txframe size

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapter 5.7.2 states that the maximum frame size
(N1) refers to the length of the information field (i.e. user payload).
However, 'txframe' stores the whole frame including frame header, checksum
and start/end flags. We also need to consider the byte stuffing overhead.
Define constant for the protocol overhead and adjust the 'txframe' size
calculation accordingly to reserve enough space for a complete mux frame
including byte stuffing for advanced option mode. Note that no byte
stuffing is applied to the start and end flag.
Also use MAX_MTU instead of MAX_MRU as this buffer is used for data
transmission.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-8-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 2e3da8a4697e..cc90b03ce005 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -73,6 +73,8 @@ module_param(debug, int, 0600);
  */
 #define MAX_MRU 1500
 #define MAX_MTU 1500
+/* SOF, ADDR, CTRL, LEN1, LEN2, ..., FCS, EOF */
+#define PROT_OVERHEAD 7
 #define	GSM_NET_TX_TIMEOUT (HZ*10)
 
 /*
@@ -2264,7 +2266,7 @@ static struct gsm_mux *gsm_alloc_mux(void)
 		kfree(gsm);
 		return NULL;
 	}
-	gsm->txframe = kmalloc(2 * MAX_MRU + 2, GFP_KERNEL);
+	gsm->txframe = kmalloc(2 * (MAX_MTU + PROT_OVERHEAD - 1), GFP_KERNEL);
 	if (gsm->txframe == NULL) {
 		kfree(gsm->buf);
 		kfree(gsm);
-- 
cgit v1.2.3


From deefc58bafb4841df7f0a0d85d89a1c819db9743 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:14 -0700
Subject: tty: n_gsm: fix wrong DLCI release order

The current DLCI release order starts with the control channel followed by
the user channels. Reverse this order to keep the control channel open
until all user channels have been released.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-9-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index cc90b03ce005..6b953dfbb155 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2146,8 +2146,8 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 	/* Finish outstanding timers, making sure they are done */
 	del_timer_sync(&gsm->t2_timer);
 
-	/* Free up any link layer users */
-	for (i = 0; i < NUM_DLCI; i++)
+	/* Free up any link layer users and finally the control channel */
+	for (i = NUM_DLCI - 1; i >= 0; i--)
 		if (gsm->dlci[i])
 			gsm_dlci_release(gsm->dlci[i]);
 	mutex_unlock(&gsm->mutex);
-- 
cgit v1.2.3


From 17eac652028501df7ea296b1d9b9c134db262b7d Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:15 -0700
Subject: tty: n_gsm: fix missing explicit ldisc flush

In gsm_cleanup_mux() the muxer is closed down and all queues are removed.
However, removing the queues is done without explicit control of the
underlying buffers. Flush those before freeing up our queues to ensure
that all outgoing queues are cleared consistently. Otherwise, a new mux
connection establishment attempt may time out while the underlying tty is
still busy sending out the remaining data from the previous connection.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-10-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 1 +
 1 file changed, 1 insertion(+)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 6b953dfbb155..1430d7f83bd2 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2152,6 +2152,7 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 			gsm_dlci_release(gsm->dlci[i]);
 	mutex_unlock(&gsm->mutex);
 	/* Now wipe the queues */
+	tty_ldisc_flush(gsm->tty);
 	list_for_each_entry_safe(txq, ntxq, &gsm->tx_list, list)
 		kfree(txq);
 	INIT_LIST_HEAD(&gsm->tx_list);
-- 
cgit v1.2.3


From d0bcdffcad5a22f202e3bf37190c0dd8c080ea92 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:16 -0700
Subject: tty: n_gsm: fix wrong command retry handling

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapter 5.7.3 states that the valid range for the
maximum number of retransmissions (N2) is from 0 to 255 (both including).
gsm_config() fails to limit this range correctly. Furthermore,
gsm_control_retransmit() handles this number incorrectly by performing
N2 - 1 retransmission attempts. Setting N2 to zero results in more than 255
retransmission attempts.
Fix the range check in gsm_config() and the value handling in
gsm_control_send() and gsm_control_retransmit() to comply with 3GPP 27.010.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-11-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 1430d7f83bd2..628bda5f0622 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1354,7 +1354,6 @@ static void gsm_control_retransmit(struct timer_list *t)
 	spin_lock_irqsave(&gsm->control_lock, flags);
 	ctrl = gsm->pending_cmd;
 	if (ctrl) {
-		gsm->cretries--;
 		if (gsm->cretries == 0) {
 			gsm->pending_cmd = NULL;
 			ctrl->error = -ETIMEDOUT;
@@ -1363,6 +1362,7 @@ static void gsm_control_retransmit(struct timer_list *t)
 			wake_up(&gsm->event);
 			return;
 		}
+		gsm->cretries--;
 		gsm_control_transmit(gsm, ctrl);
 		mod_timer(&gsm->t2_timer, jiffies + gsm->t2 * HZ / 100);
 	}
@@ -1403,7 +1403,7 @@ retry:
 
 	/* If DLCI0 is in ADM mode skip retries, it won't respond */
 	if (gsm->dlci[0]->mode == DLCI_MODE_ADM)
-		gsm->cretries = 1;
+		gsm->cretries = 0;
 	else
 		gsm->cretries = gsm->n2;
 
@@ -2343,7 +2343,7 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
 	/* Check the MRU/MTU range looks sane */
 	if (c->mru > MAX_MRU || c->mtu > MAX_MTU || c->mru < 8 || c->mtu < 8)
 		return -EINVAL;
-	if (c->n2 < 3)
+	if (c->n2 > 255)
 		return -EINVAL;
 	if (c->encapsulation > 1)	/* Basic, advanced, no I */
 		return -EINVAL;
-- 
cgit v1.2.3


From 398867f59f956985f4c324f173eff7b946e14bd8 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:17 -0700
Subject: tty: n_gsm: fix wrong command frame length field encoding

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapter 5.4.6.1 states that each command frame shall
be made up from type, length and value. Looking for example in chapter
5.4.6.3.5 at the description for the encoding of a flow control on command
it becomes obvious, that the type and length field is always present
whereas the value may be zero bytes long. The current implementation omits
the length field if the value is not present. This is wrong.
Correct this by always sending the length in gsm_control_transmit().
So far only the modem status command (MSC) has included a value and encoded
its length directly. Therefore, also change gsmtty_modem_update().

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-12-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 628bda5f0622..903278145078 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1327,11 +1327,12 @@ static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
 
 static void gsm_control_transmit(struct gsm_mux *gsm, struct gsm_control *ctrl)
 {
-	struct gsm_msg *msg = gsm_data_alloc(gsm, 0, ctrl->len + 1, gsm->ftype);
+	struct gsm_msg *msg = gsm_data_alloc(gsm, 0, ctrl->len + 2, gsm->ftype);
 	if (msg == NULL)
 		return;
-	msg->data[0] = (ctrl->cmd << 1) | 2 | EA;	/* command */
-	memcpy(msg->data + 1, ctrl->data, ctrl->len);
+	msg->data[0] = (ctrl->cmd << 1) | CR | EA;	/* command */
+	msg->data[1] = (ctrl->len << 1) | EA;
+	memcpy(msg->data + 2, ctrl->data, ctrl->len);
 	gsm_data_queue(gsm->dlci[0], msg);
 }
 
@@ -2957,19 +2958,17 @@ static struct tty_ldisc_ops tty_ldisc_packet = {
 
 static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk)
 {
-	u8 modembits[5];
+	u8 modembits[3];
 	struct gsm_control *ctrl;
 	int len = 2;
 
-	if (brk)
+	modembits[0] = (dlci->addr << 2) | 2 | EA;  /* DLCI, Valid, EA */
+	modembits[1] = (gsm_encode_modem(dlci) << 1) | EA;
+	if (brk) {
+		modembits[2] = (brk << 4) | 2 | EA; /* Length, Break, EA */
 		len++;
-
-	modembits[0] = len << 1 | EA;		/* Data bytes */
-	modembits[1] = dlci->addr << 2 | 3;	/* DLCI, EA, 1 */
-	modembits[2] = gsm_encode_modem(dlci) << 1 | EA;
-	if (brk)
-		modembits[3] = brk << 4 | 2 | EA;	/* Valid, EA */
-	ctrl = gsm_control_send(dlci->gsm, CMD_MSC, modembits, len + 1);
+	}
+	ctrl = gsm_control_send(dlci->gsm, CMD_MSC, modembits, len);
 	if (ctrl == NULL)
 		return -ENOMEM;
 	return gsm_control_wait(dlci->gsm, ctrl);
-- 
cgit v1.2.3


From 317f86af7f5d19f286ed2d181cbaef4a188c7f19 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:18 -0700
Subject: tty: n_gsm: fix wrong signal octets encoding in MSC

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. The value of the modem status command (MSC) frame
contains an address field, control signal and optional break signal octet.
The address field is encoded as described in chapter 5.2.1.2 with only one
octet (may be extended to more in future versions of the standard). Whereas
the control signal and break signal octet are always one byte each. This is
strange at first glance as it makes the EA bit redundant. However, the same
two octets are also encoded as header in convergence layer type 2 as
described in chapter 5.5.2. No header length field is given and the only
way to test if there is an optional break signal octet is via the EA flag
which extends the control signal octet with a break signal octet. Now it
becomes obvious how the EA bit for those two octets shall be encoded in the
MSC frame. The current implementation treats the signal octet different for
MSC frame and convergence layer type 2 header even though the standard
describes it for both in the same way.
Use the EA bit to encode the signal octets not only in the convergence
layer type 2 header but also in the MSC frame in the same way with either
1 or 2 bytes in case of an optional break signal. Adjust the receiving path
accordingly in gsm_control_modem().

Fixes: 3ac06b905655 ("tty: n_gsm: Fix for modems with brk in modem status control")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-13-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 903278145078..23418ee93156 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1094,7 +1094,6 @@ static void gsm_control_modem(struct gsm_mux *gsm, const u8 *data, int clen)
 {
 	unsigned int addr = 0;
 	unsigned int modem = 0;
-	unsigned int brk = 0;
 	struct gsm_dlci *dlci;
 	int len = clen;
 	int slen;
@@ -1124,17 +1123,8 @@ static void gsm_control_modem(struct gsm_mux *gsm, const u8 *data, int clen)
 			return;
 	}
 	len--;
-	if (len > 0) {
-		while (gsm_read_ea(&brk, *dp++) == 0) {
-			len--;
-			if (len == 0)
-				return;
-		}
-		modem <<= 7;
-		modem |= (brk & 0x7f);
-	}
 	tty = tty_port_tty_get(&dlci->port);
-	gsm_process_modem(tty, dlci, modem, slen);
+	gsm_process_modem(tty, dlci, modem, slen - len);
 	if (tty) {
 		tty_wakeup(tty);
 		tty_kref_put(tty);
@@ -2963,8 +2953,10 @@ static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk)
 	int len = 2;
 
 	modembits[0] = (dlci->addr << 2) | 2 | EA;  /* DLCI, Valid, EA */
-	modembits[1] = (gsm_encode_modem(dlci) << 1) | EA;
-	if (brk) {
+	if (!brk) {
+		modembits[1] = (gsm_encode_modem(dlci) << 1) | EA;
+	} else {
+		modembits[1] = gsm_encode_modem(dlci) << 1;
 		modembits[2] = (brk << 4) | 2 | EA; /* Length, Break, EA */
 		len++;
 	}
-- 
cgit v1.2.3


From 1adf6fee58ca25fb6720b8d34c919dcf5425cc9c Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:19 -0700
Subject: tty: n_gsm: fix missing tty wakeup in convergence layer type 2

gsm_control_modem() informs the virtual tty that more data can be written
after receiving a control signal octet via modem status command (MSC).
However, gsm_dlci_data() fails to do the same after receiving a control
signal octet from the convergence layer type 2 header.
Add tty_wakeup() in gsm_dlci_data() for convergence layer type 2 to fix
this.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-14-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 1 +
 1 file changed, 1 insertion(+)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 23418ee93156..f3fb66be8513 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1615,6 +1615,7 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
 		tty = tty_port_tty_get(port);
 		if (tty) {
 			gsm_process_modem(tty, dlci, modem, slen);
+			tty_wakeup(tty);
 			tty_kref_put(tty);
 		}
 		fallthrough;
-- 
cgit v1.2.3


From 73029a4d7161f8b6c0934553145ef574d2d0c645 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:22 -0700
Subject: tty: n_gsm: fix reset fifo race condition

gsmtty_write() and gsm_dlci_data_output() properly guard the fifo access.
However, gsm_dlci_close() and gsmtty_flush_buffer() modifies the fifo but
do not guard this.
Add a guard here to prevent race conditions on parallel writes to the fifo.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-17-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index f3fb66be8513..15be4a235783 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1442,13 +1442,17 @@ static int gsm_control_wait(struct gsm_mux *gsm, struct gsm_control *control)
 
 static void gsm_dlci_close(struct gsm_dlci *dlci)
 {
+	unsigned long flags;
+
 	del_timer(&dlci->t1);
 	if (debug & 8)
 		pr_debug("DLCI %d goes closed.\n", dlci->addr);
 	dlci->state = DLCI_CLOSED;
 	if (dlci->addr != 0) {
 		tty_port_tty_hangup(&dlci->port, false);
+		spin_lock_irqsave(&dlci->lock, flags);
 		kfifo_reset(&dlci->fifo);
+		spin_unlock_irqrestore(&dlci->lock, flags);
 		/* Ensure that gsmtty_open() can return. */
 		tty_port_set_initialized(&dlci->port, 0);
 		wake_up_interruptible(&dlci->port.open_wait);
@@ -3148,13 +3152,17 @@ static unsigned int gsmtty_chars_in_buffer(struct tty_struct *tty)
 static void gsmtty_flush_buffer(struct tty_struct *tty)
 {
 	struct gsm_dlci *dlci = tty->driver_data;
+	unsigned long flags;
+
 	if (dlci->state == DLCI_CLOSED)
 		return;
 	/* Caution needed: If we implement reliable transport classes
 	   then the data being transmitted can't simply be junked once
 	   it has first hit the stack. Until then we can just blow it
 	   away */
+	spin_lock_irqsave(&dlci->lock, flags);
 	kfifo_reset(&dlci->fifo);
+	spin_unlock_irqrestore(&dlci->lock, flags);
 	/* Need to unhook this DLCI from the transmit queue logic */
 }
 
-- 
cgit v1.2.3


From ff9166c623704337bd6fe66fce2838d9768a6634 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Thu, 14 Apr 2022 02:42:25 -0700
Subject: tty: n_gsm: fix incorrect UA handling

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapter 5.4.4.2 states that any received unnumbered
acknowledgment (UA) with its poll/final (PF) bit set to 0 shall be
discarded. Currently, all UA frame are handled in the same way regardless
of the PF bit. This does not comply with the standard.
Remove the UA case in gsm_queue() to process only UA frames with PF bit set
to 1 to abide the standard.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-20-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 1 -
 1 file changed, 1 deletion(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 15be4a235783..e440c7f6d20e 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1865,7 +1865,6 @@ static void gsm_queue(struct gsm_mux *gsm)
 			}
 		}
 		break;
-	case UA:
 	case UA|PF:
 		if (cr == 0 || dlci == NULL)
 			break;
-- 
cgit v1.2.3


From 48473802506d2d6151f59e0e764932b33b53cb3b Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Wed, 20 Apr 2022 03:13:44 -0700
Subject: tty: n_gsm: fix missing update of modem controls after DLCI open

Currently the peer is not informed about the initial state of the modem
control lines after a new DLCI has been opened.
Fix this by sending the initial modem control line states after DLCI open.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220420101346.3315-1-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index e440c7f6d20e..979dc9151383 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -370,6 +370,7 @@ static const u8 gsm_fcs8[256] = {
 #define GOOD_FCS	0xCF
 
 static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len);
+static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk);
 
 /**
  *	gsm_fcs_add	-	update FCS
@@ -1483,6 +1484,9 @@ static void gsm_dlci_open(struct gsm_dlci *dlci)
 		pr_debug("DLCI %d goes open.\n", dlci->addr);
 	/* Register gsmtty driver,report gsmtty dev add uevent for user */
 	tty_register_device(gsm_tty_driver, dlci->addr, NULL);
+	/* Send current modem state */
+	if (dlci->addr)
+		gsmtty_modem_update(dlci, 0);
 	wake_up(&dlci->gsm->event);
 }
 
-- 
cgit v1.2.3


From a8c5b8255f8a9acd58a4b15ff1c14cd6effd114b Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Fri, 22 Apr 2022 00:10:23 -0700
Subject: tty: n_gsm: fix broken virtual tty handling

Dynamic virtual tty registration was introduced to allow the user to handle
these cases with uevent rules. The following commits relate to this:
Commit 5b87686e3203 ("tty: n_gsm: Modify gsmtty driver register method when config requester")
Commit 0b91b5332368 ("tty: n_gsm: Save dlci address open status when config requester")
Commit 46292622ad73 ("tty: n_gsm: clean up indenting in gsm_queue()")

However, the following behavior can be seen with this implementation:
- n_gsm ldisc is activated via ioctl
- all configuration parameters are set to their default value (initiator=0)
- the mux gets activated and attached and gsmtty0 is being registered in
  in gsm_dlci_open() after DLCI 0 was established (DLCI 0 is the control
  channel)
- the user configures n_gsm via ioctl GSMIOC_SETCONF as initiator
- this re-attaches the n_gsm mux
- no new gsmtty devices are registered in gsmld_attach_gsm() because the
  mux is already active
- the initiator side registered only the control channel as gsmtty0
  (which should never happen) and no user channel tty

The commits above make it impossible to operate the initiator side as no
user channel tty is or will be available.
On the other hand, this behavior will make it also impossible to allow DLCI
parameter negotiation on responder side in the future. The responder side
first needs to provide a device for the application before the application
can set its parameters of the associated DLCI via ioctl.
Note that the user application is still able to detect a link establishment
without relaying to uevent by waiting for DTR open on responder side. This
is the same behavior as on a physical serial interface. And on initiator
side a tty hangup can be detected if a link establishment request failed.

Revert the commits above completely to always register all user channels
and no control channel after mux attachment. No other changes are made.

Fixes: 5b87686e3203 ("tty: n_gsm: Modify gsmtty driver register method when config requester")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220422071025.5490-1-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 87 +++++++++--------------------------------------------
 1 file changed, 15 insertions(+), 72 deletions(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 979dc9151383..99fe54247a87 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -272,10 +272,6 @@ static DEFINE_SPINLOCK(gsm_mux_lock);
 
 static struct tty_driver *gsm_tty_driver;
 
-/* Save dlci open address */
-static int addr_open[256] = { 0 };
-/* Save dlci open count */
-static int addr_cnt;
 /*
  *	This section of the driver logic implements the GSM encodings
  *	both the basic and the 'advanced'. Reliable transport is not
@@ -1185,7 +1181,6 @@ static void gsm_control_rls(struct gsm_mux *gsm, const u8 *data, int clen)
 }
 
 static void gsm_dlci_begin_close(struct gsm_dlci *dlci);
-static void gsm_dlci_close(struct gsm_dlci *dlci);
 
 /**
  *	gsm_control_message	-	DLCI 0 control processing
@@ -1204,28 +1199,15 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
 {
 	u8 buf[1];
 	unsigned long flags;
-	struct gsm_dlci *dlci;
-	int i;
-	int address;
 
 	switch (command) {
 	case CMD_CLD: {
-		if (addr_cnt > 0) {
-			for (i = 0; i < addr_cnt; i++) {
-				address = addr_open[i];
-				dlci = gsm->dlci[address];
-				gsm_dlci_close(dlci);
-				addr_open[i] = 0;
-			}
-		}
+		struct gsm_dlci *dlci = gsm->dlci[0];
 		/* Modem wishes to close down */
-		dlci = gsm->dlci[0];
 		if (dlci) {
 			dlci->dead = true;
 			gsm->dead = true;
-			gsm_dlci_close(dlci);
-			addr_cnt = 0;
-			gsm_response(gsm, 0, UA|PF);
+			gsm_dlci_begin_close(dlci);
 		}
 		}
 		break;
@@ -1459,8 +1441,6 @@ static void gsm_dlci_close(struct gsm_dlci *dlci)
 		wake_up_interruptible(&dlci->port.open_wait);
 	} else
 		dlci->gsm->dead = true;
-	/* Unregister gsmtty driver,report gsmtty dev remove uevent for user */
-	tty_unregister_device(gsm_tty_driver, dlci->addr);
 	wake_up(&dlci->gsm->event);
 	/* A DLCI 0 close is a MUX termination so we need to kick that
 	   back to userspace somehow */
@@ -1482,8 +1462,6 @@ static void gsm_dlci_open(struct gsm_dlci *dlci)
 	dlci->state = DLCI_OPEN;
 	if (debug & 8)
 		pr_debug("DLCI %d goes open.\n", dlci->addr);
-	/* Register gsmtty driver,report gsmtty dev add uevent for user */
-	tty_register_device(gsm_tty_driver, dlci->addr, NULL);
 	/* Send current modem state */
 	if (dlci->addr)
 		gsmtty_modem_update(dlci, 0);
@@ -1794,7 +1772,6 @@ static void gsm_queue(struct gsm_mux *gsm)
 	struct gsm_dlci *dlci;
 	u8 cr;
 	int address;
-	int i, j, k, address_tmp;
 
 	if (gsm->fcs != GOOD_FCS) {
 		gsm->bad_fcs++;
@@ -1826,11 +1803,6 @@ static void gsm_queue(struct gsm_mux *gsm)
 		else {
 			gsm_response(gsm, address, UA|PF);
 			gsm_dlci_open(dlci);
-			/* Save dlci open address */
-			if (address) {
-				addr_open[addr_cnt] = address;
-				addr_cnt++;
-			}
 		}
 		break;
 	case DISC|PF:
@@ -1841,33 +1813,8 @@ static void gsm_queue(struct gsm_mux *gsm)
 			return;
 		}
 		/* Real close complete */
-		if (!address) {
-			if (addr_cnt > 0) {
-				for (i = 0; i < addr_cnt; i++) {
-					address = addr_open[i];
-					dlci = gsm->dlci[address];
-					gsm_dlci_close(dlci);
-					addr_open[i] = 0;
-				}
-			}
-			dlci = gsm->dlci[0];
-			gsm_dlci_close(dlci);
-			addr_cnt = 0;
-			gsm_response(gsm, 0, UA|PF);
-		} else {
-			gsm_response(gsm, address, UA|PF);
-			gsm_dlci_close(dlci);
-			/* clear dlci address */
-			for (j = 0; j < addr_cnt; j++) {
-				address_tmp = addr_open[j];
-				if (address_tmp == address) {
-					for (k = j; k < addr_cnt; k++)
-						addr_open[k] = addr_open[k+1];
-					addr_cnt--;
-					break;
-				}
-			}
-		}
+		gsm_response(gsm, address, UA|PF);
+		gsm_dlci_close(dlci);
 		break;
 	case UA|PF:
 		if (cr == 0 || dlci == NULL)
@@ -2451,19 +2398,17 @@ static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 	else {
 		/* Don't register device 0 - this is the control channel and not
 		   a usable tty interface */
-		if (gsm->initiator) {
-			base = mux_num_to_base(gsm); /* Base for this MUX */
-			for (i = 1; i < NUM_DLCI; i++) {
-				struct device *dev;
+		base = mux_num_to_base(gsm); /* Base for this MUX */
+		for (i = 1; i < NUM_DLCI; i++) {
+			struct device *dev;
 
-				dev = tty_register_device(gsm_tty_driver,
+			dev = tty_register_device(gsm_tty_driver,
 							base + i, NULL);
-				if (IS_ERR(dev)) {
-					for (i--; i >= 1; i--)
-						tty_unregister_device(gsm_tty_driver,
-									base + i);
-					return PTR_ERR(dev);
-				}
+			if (IS_ERR(dev)) {
+				for (i--; i >= 1; i--)
+					tty_unregister_device(gsm_tty_driver,
+								base + i);
+				return PTR_ERR(dev);
 			}
 		}
 	}
@@ -2485,10 +2430,8 @@ static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 	int i;
 
 	WARN_ON(tty != gsm->tty);
-	if (gsm->initiator) {
-		for (i = 1; i < NUM_DLCI; i++)
-			tty_unregister_device(gsm_tty_driver, base + i);
-	}
+	for (i = 1; i < NUM_DLCI; i++)
+		tty_unregister_device(gsm_tty_driver, base + i);
 	tty_kref_put(gsm->tty);
 	gsm->tty = NULL;
 }
-- 
cgit v1.2.3


From c19ffe00fed6bb423d81406d2a7e5793074c7d83 Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Fri, 22 Apr 2022 00:10:24 -0700
Subject: tty: n_gsm: fix invalid use of MSC in advanced option

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapter 5.4.6.3.7 states that the Modem Status
Command (MSC) shall only be used if the basic option was chosen.
The current implementation uses MSC frames even if advanced option was
chosen to inform the peer about modem line state updates. A standard
conform peer may choose to discard these frames in advanced option mode.
Furthermore, gsmtty_modem_update() is not part of the 'tty_operations'
functions despite its name.
Rename gsmtty_modem_update() to gsm_modem_update() to clarify this. Split
its function into gsm_modem_upd_via_data() and gsm_modem_upd_via_msc()
depending on the encoding and adaption. Introduce gsm_dlci_modem_output()
as adaption of gsm_dlci_data_output() to encode and queue empty frames in
advanced option mode. Use it in gsm_modem_upd_via_data().
gsm_modem_upd_via_msc() is based on the initial gsmtty_modem_update()
function which used only MSC frames to update modem states.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220422071025.5490-2-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 125 ++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 117 insertions(+), 8 deletions(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 99fe54247a87..570f0b8b7576 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -366,7 +366,7 @@ static const u8 gsm_fcs8[256] = {
 #define GOOD_FCS	0xCF
 
 static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len);
-static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk);
+static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk);
 
 /**
  *	gsm_fcs_add	-	update FCS
@@ -914,6 +914,63 @@ static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
 	return size;
 }
 
+/**
+ *	gsm_dlci_modem_output	-	try and push modem status out of a DLCI
+ *	@gsm: mux
+ *	@dlci: the DLCI to pull modem status from
+ *	@brk: break signal
+ *
+ *	Push an empty frame in to the transmit queue to update the modem status
+ *	bits and to transmit an optional break.
+ *
+ *	Caller must hold the tx_lock of the mux.
+ */
+
+static int gsm_dlci_modem_output(struct gsm_mux *gsm, struct gsm_dlci *dlci,
+				 u8 brk)
+{
+	u8 *dp = NULL;
+	struct gsm_msg *msg;
+	int size;
+
+	/* for modem bits without break data */
+	if (dlci->adaption == 1) {
+		size = 0;
+	} else if (dlci->adaption == 2) {
+		size = 1;
+		if (brk > 0)
+			size++;
+	} else {
+		pr_err("%s: unsupported adaption %d\n", __func__,
+		       dlci->adaption);
+	}
+
+	msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype);
+	if (!msg) {
+		pr_err("%s: gsm_data_alloc error", __func__);
+		return -ENOMEM;
+	}
+	dp = msg->data;
+	switch (dlci->adaption) {
+	case 1: /* Unstructured */
+		break;
+	case 2: /* Unstructured with modem bits. */
+		if (brk == 0) {
+			*dp++ = (gsm_encode_modem(dlci) << 1) | EA;
+		} else {
+			*dp++ = gsm_encode_modem(dlci) << 1;
+			*dp++ = (brk << 4) | 2 | EA; /* Length, Break, EA */
+		}
+		break;
+	default:
+		/* Handled above */
+		break;
+	}
+
+	__gsm_data_queue(dlci, msg);
+	return size;
+}
+
 /**
  *	gsm_dlci_data_sweep		-	look for data to send
  *	@gsm: the GSM mux
@@ -1464,7 +1521,7 @@ static void gsm_dlci_open(struct gsm_dlci *dlci)
 		pr_debug("DLCI %d goes open.\n", dlci->addr);
 	/* Send current modem state */
 	if (dlci->addr)
-		gsmtty_modem_update(dlci, 0);
+		gsm_modem_update(dlci, 0);
 	wake_up(&dlci->gsm->event);
 }
 
@@ -2897,12 +2954,43 @@ static struct tty_ldisc_ops tty_ldisc_packet = {
 
 #define TX_SIZE		512
 
-static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk)
+/**
+ *	gsm_modem_upd_via_data	-	send modem bits via convergence layer
+ *	@dlci: channel
+ *	@brk: break signal
+ *
+ *	Send an empty frame to signal mobile state changes and to transmit the
+ *	break signal for adaption 2.
+ */
+
+static void gsm_modem_upd_via_data(struct gsm_dlci *dlci, u8 brk)
+{
+	struct gsm_mux *gsm = dlci->gsm;
+	unsigned long flags;
+
+	if (dlci->state != DLCI_OPEN || dlci->adaption != 2)
+		return;
+
+	spin_lock_irqsave(&gsm->tx_lock, flags);
+	gsm_dlci_modem_output(gsm, dlci, brk);
+	spin_unlock_irqrestore(&gsm->tx_lock, flags);
+}
+
+/**
+ *	gsm_modem_upd_via_msc	-	send modem bits via control frame
+ *	@dlci: channel
+ *	@brk: break signal
+ */
+
+static int gsm_modem_upd_via_msc(struct gsm_dlci *dlci, u8 brk)
 {
 	u8 modembits[3];
 	struct gsm_control *ctrl;
 	int len = 2;
 
+	if (dlci->gsm->encoding != 0)
+		return 0;
+
 	modembits[0] = (dlci->addr << 2) | 2 | EA;  /* DLCI, Valid, EA */
 	if (!brk) {
 		modembits[1] = (gsm_encode_modem(dlci) << 1) | EA;
@@ -2917,6 +3005,27 @@ static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk)
 	return gsm_control_wait(dlci->gsm, ctrl);
 }
 
+/**
+ *	gsm_modem_update	-	send modem status line state
+ *	@dlci: channel
+ *	@brk: break signal
+ */
+
+static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk)
+{
+	if (dlci->adaption == 2) {
+		/* Send convergence layer type 2 empty data frame. */
+		gsm_modem_upd_via_data(dlci, brk);
+		return 0;
+	} else if (dlci->gsm->encoding == 0) {
+		/* Send as MSC control message. */
+		return gsm_modem_upd_via_msc(dlci, brk);
+	}
+
+	/* Modem status lines are not supported. */
+	return -EPROTONOSUPPORT;
+}
+
 static int gsm_carrier_raised(struct tty_port *port)
 {
 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
@@ -2949,7 +3058,7 @@ static void gsm_dtr_rts(struct tty_port *port, int onoff)
 		modem_tx &= ~(TIOCM_DTR | TIOCM_RTS);
 	if (modem_tx != dlci->modem_tx) {
 		dlci->modem_tx = modem_tx;
-		gsmtty_modem_update(dlci, 0);
+		gsm_modem_update(dlci, 0);
 	}
 }
 
@@ -3140,7 +3249,7 @@ static int gsmtty_tiocmset(struct tty_struct *tty,
 
 	if (modem_tx != dlci->modem_tx) {
 		dlci->modem_tx = modem_tx;
-		return gsmtty_modem_update(dlci, 0);
+		return gsm_modem_update(dlci, 0);
 	}
 	return 0;
 }
@@ -3201,7 +3310,7 @@ static void gsmtty_throttle(struct tty_struct *tty)
 		dlci->modem_tx &= ~TIOCM_RTS;
 	dlci->throttled = true;
 	/* Send an MSC with RTS cleared */
-	gsmtty_modem_update(dlci, 0);
+	gsm_modem_update(dlci, 0);
 }
 
 static void gsmtty_unthrottle(struct tty_struct *tty)
@@ -3213,7 +3322,7 @@ static void gsmtty_unthrottle(struct tty_struct *tty)
 		dlci->modem_tx |= TIOCM_RTS;
 	dlci->throttled = false;
 	/* Send an MSC with RTS set */
-	gsmtty_modem_update(dlci, 0);
+	gsm_modem_update(dlci, 0);
 }
 
 static int gsmtty_break_ctl(struct tty_struct *tty, int state)
@@ -3231,7 +3340,7 @@ static int gsmtty_break_ctl(struct tty_struct *tty, int state)
 		if (encode > 0x0F)
 			encode = 0x0F;	/* Best effort */
 	}
-	return gsmtty_modem_update(dlci, encode);
+	return gsm_modem_update(dlci, encode);
 }
 
 static void gsmtty_cleanup(struct tty_struct *tty)
-- 
cgit v1.2.3


From f4f7d63287217ba25e5c80f5faae5e4f7118790e Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Fri, 22 Apr 2022 00:10:25 -0700
Subject: tty: n_gsm: fix software flow control handling

n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
the newer 27.010 here. Chapter 5.4.8.1 states that XON/XOFF characters
shall be used instead of Fcon/Fcoff command in advanced option mode to
handle flow control. Chapter 5.4.8.2 describes how XON/XOFF characters
shall be handled. Basic option mode only used Fcon/Fcoff commands and no
XON/XOFF characters. These are treated as data bytes here.
The current implementation uses the gsm_mux field 'constipated' to handle
flow control from the remote peer and the gsm_dlci field 'constipated' to
handle flow control from each DLCI. The later is unrelated to this patch.
The gsm_mux field is correctly set for Fcon/Fcoff commands in
gsm_control_message(). However, the same is not true for XON/XOFF
characters in gsm1_receive().
Disable software flow control handling in the tty to allow explicit
handling by n_gsm.
Add the missing handling in advanced option mode for gsm_mux in
gsm1_receive() to comply with the standard.

This patch depends on the following commit:
Commit 8838b2af23ca ("tty: n_gsm: fix SW flow control encoding/handling")

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220422071025.5490-3-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 570f0b8b7576..8652308c187f 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -232,6 +232,7 @@ struct gsm_mux {
 	int initiator;			/* Did we initiate connection */
 	bool dead;			/* Has the mux been shut down */
 	struct gsm_dlci *dlci[NUM_DLCI];
+	int old_c_iflag;		/* termios c_iflag value before attach */
 	bool constipated;		/* Asked by remote to shut up */
 
 	spinlock_t tx_lock;
@@ -2022,6 +2023,16 @@ static void gsm0_receive(struct gsm_mux *gsm, unsigned char c)
 
 static void gsm1_receive(struct gsm_mux *gsm, unsigned char c)
 {
+	/* handle XON/XOFF */
+	if ((c & ISO_IEC_646_MASK) == XON) {
+		gsm->constipated = true;
+		return;
+	} else if ((c & ISO_IEC_646_MASK) == XOFF) {
+		gsm->constipated = false;
+		/* Kick the link in case it is idling */
+		gsm_data_kick(gsm, NULL);
+		return;
+	}
 	if (c == GSM1_SOF) {
 		/* EOF is only valid in frame if we have got to the data state */
 		if (gsm->state == GSM_DATA) {
@@ -2449,6 +2460,9 @@ static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 	int ret, i;
 
 	gsm->tty = tty_kref_get(tty);
+	/* Turn off tty XON/XOFF handling to handle it explicitly. */
+	gsm->old_c_iflag = tty->termios.c_iflag;
+	tty->termios.c_iflag &= (IXON | IXOFF);
 	ret =  gsm_activate_mux(gsm);
 	if (ret != 0)
 		tty_kref_put(gsm->tty);
@@ -2489,6 +2503,8 @@ static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 	WARN_ON(tty != gsm->tty);
 	for (i = 1; i < NUM_DLCI; i++)
 		tty_unregister_device(gsm_tty_driver, base + i);
+	/* Restore tty XON/XOFF handling. */
+	gsm->tty->termios.c_iflag = gsm->old_c_iflag;
 	tty_kref_put(gsm->tty);
 	gsm->tty = NULL;
 }
-- 
cgit v1.2.3


From 19317433057dc1f2ca9a975e4e6b547282c2a5ef Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@siemens.com>
Date: Mon, 25 Apr 2022 03:47:26 -0700
Subject: tty: n_gsm: fix sometimes uninitialized warning in
 gsm_dlci_modem_output()

'size' may be used uninitialized in gsm_dlci_modem_output() if called with
an adaption that is neither 1 nor 2. The function is currently only called
by gsm_modem_upd_via_data() and only for adaption 2.
Properly handle every invalid case by returning -EINVAL to silence the
compiler warning and avoid future regressions.

Fixes: c19ffe00fed6 ("tty: n_gsm: fix invalid use of MSC in advanced option")
Cc: stable@vger.kernel.org
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220425104726.7986-1-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

(limited to 'drivers/tty/n_gsm.c')

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 8652308c187f..a38b922bcbc1 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -932,18 +932,21 @@ static int gsm_dlci_modem_output(struct gsm_mux *gsm, struct gsm_dlci *dlci,
 {
 	u8 *dp = NULL;
 	struct gsm_msg *msg;
-	int size;
+	int size = 0;
 
 	/* for modem bits without break data */
-	if (dlci->adaption == 1) {
-		size = 0;
-	} else if (dlci->adaption == 2) {
-		size = 1;
+	switch (dlci->adaption) {
+	case 1: /* Unstructured */
+		break;
+	case 2: /* Unstructured with modem bits. */
+		size++;
 		if (brk > 0)
 			size++;
-	} else {
+		break;
+	default:
 		pr_err("%s: unsupported adaption %d\n", __func__,
 		       dlci->adaption);
+		return -EINVAL;
 	}
 
 	msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype);
-- 
cgit v1.2.3