treewide: Convert del_timer*() to timer_shutdown*()

Due to several bugs caused by timers being re-armed after they are
shutdown and just before they are freed, a new state of timers was added
called "shutdown".  After a timer is set to this state, then it can no
longer be re-armed.

The following script was run to find all the trivial locations where
del_timer() or del_timer_sync() is called in the same function that the
object holding the timer is freed.  It also ignores any locations where
the timer->function is modified between the del_timer*() and the free(),
as that is not considered a "trivial" case.

This was created by using a coccinelle script and the following
commands:

    $ cat timer.cocci
    @@
    expression ptr, slab;
    identifier timer, rfield;
    @@
    (
    -       del_timer(&ptr->timer);
    +       timer_shutdown(&ptr->timer);
    |
    -       del_timer_sync(&ptr->timer);
    +       timer_shutdown_sync(&ptr->timer);
    )
      ... when strict
          when != ptr->timer
    (
            kfree_rcu(ptr, rfield);
    |
            kmem_cache_free(slab, ptr);
    |
            kfree(ptr);
    )

    $ spatch timer.cocci . > /tmp/t.patch
    $ patch -p1 < /tmp/t.patch

Link: https://lore.kernel.org/lkml/20221123201306.823305113@linutronix.de/
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Pavel Machek <pavel@ucw.cz> [ LED ]
Acked-by: Kalle Valo <kvalo@kernel.org> [ wireless ]
Acked-by: Paolo Abeni <pabeni@redhat.com> [ networking ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 2 insertions, 2 deletions

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index daf12132deb1..348d85c13f91 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2444,7 +2444,7 @@ static void gsm_dlci_free(struct tty_port *port)
 {
 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
 
-	del_timer_sync(&dlci->t1);
+	timer_shutdown_sync(&dlci->t1);
 	dlci->gsm->dlci[dlci->addr] = NULL;
 	kfifo_free(&dlci->fifo);
 	while ((dlci->skb = skb_dequeue(&dlci->skb_list)))
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index d2b2720db6ca..b6e70c5cfa17 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -1003,7 +1003,7 @@ static void sysrq_disconnect(struct input_handle *handle)
 
 	input_close_device(handle);
 	cancel_work_sync(&sysrq->reinject_work);
-	del_timer_sync(&sysrq->keyreset_timer);
+	timer_shutdown_sync(&sysrq->keyreset_timer);
 	input_unregister_handle(handle);
 	kfree(sysrq);
 }