diff options
author | Takashi Iwai <tiwai@suse.de> | 2016-11-17 10:49:31 +0100 |
---|---|---|
committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-11-23 21:04:26 -0200 |
commit | 22a1e7783e173ab3d86018eb590107d68df46c11 (patch) | |
tree | 3beaea52d877cfab058a52b97a2e2f4d6f170b4e | |
parent | 9c763584b7c8911106bb77af7e648bef09af9d80 (diff) | |
download | linux-22a1e7783e173ab3d86018eb590107d68df46c11.tar.bz2 |
xc2028: Fix use-after-free bug properly
The commit 8dfbcc4351a0 ("[media] xc2028: avoid use after free") tried
to address the reported use-after-free by clearing the reference.
However, it's clearing the wrong pointer; it sets NULL to
priv->ctrl.fname, but it's anyway overwritten by the next line
memcpy(&priv->ctrl, p, sizeof(priv->ctrl)).
OTOH, the actual code accessing the freed string is the strcmp() call
with priv->fname:
if (!firmware_name[0] && p->fname &&
priv->fname && strcmp(p->fname, priv->fname))
free_firmware(priv);
where priv->fname points to the previous file name, and this was
already freed by kfree().
For fixing the bug properly, this patch does the following:
- Keep the copy of firmware file name in only priv->fname,
priv->ctrl.fname isn't changed;
- The allocation is done only when the firmware gets loaded;
- The kfree() is called in free_firmware() commonly
Fixes: commit 8dfbcc4351a0 ('[media] xc2028: avoid use after free')
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
-rw-r--r-- | drivers/media/tuners/tuner-xc2028.c | 37 |
1 files changed, 16 insertions, 21 deletions
diff --git a/drivers/media/tuners/tuner-xc2028.c b/drivers/media/tuners/tuner-xc2028.c index 317ef63ee789..8d96a22647b3 100644 --- a/drivers/media/tuners/tuner-xc2028.c +++ b/drivers/media/tuners/tuner-xc2028.c @@ -281,6 +281,14 @@ static void free_firmware(struct xc2028_data *priv) int i; tuner_dbg("%s called\n", __func__); + /* free allocated f/w string */ + if (priv->fname != firmware_name) + kfree(priv->fname); + priv->fname = NULL; + + priv->state = XC2028_NO_FIRMWARE; + memset(&priv->cur_fw, 0, sizeof(priv->cur_fw)); + if (!priv->firm) return; @@ -291,9 +299,6 @@ static void free_firmware(struct xc2028_data *priv) priv->firm = NULL; priv->firm_size = 0; - priv->state = XC2028_NO_FIRMWARE; - - memset(&priv->cur_fw, 0, sizeof(priv->cur_fw)); } static int load_all_firmwares(struct dvb_frontend *fe, @@ -884,9 +889,8 @@ read_not_reliable: return 0; fail: - priv->state = XC2028_NO_FIRMWARE; + free_firmware(priv); - memset(&priv->cur_fw, 0, sizeof(priv->cur_fw)); if (retry_count < 8) { msleep(50); retry_count++; @@ -1332,11 +1336,8 @@ static int xc2028_dvb_release(struct dvb_frontend *fe) mutex_lock(&xc2028_list_mutex); /* only perform final cleanup if this is the last instance */ - if (hybrid_tuner_report_instance_count(priv) == 1) { + if (hybrid_tuner_report_instance_count(priv) == 1) free_firmware(priv); - kfree(priv->ctrl.fname); - priv->ctrl.fname = NULL; - } if (priv) hybrid_tuner_release_state(priv); @@ -1399,19 +1400,8 @@ static int xc2028_set_config(struct dvb_frontend *fe, void *priv_cfg) /* * Copy the config data. - * For the firmware name, keep a local copy of the string, - * in order to avoid troubles during device release. */ - kfree(priv->ctrl.fname); - priv->ctrl.fname = NULL; memcpy(&priv->ctrl, p, sizeof(priv->ctrl)); - if (p->fname) { - priv->ctrl.fname = kstrdup(p->fname, GFP_KERNEL); - if (priv->ctrl.fname == NULL) { - rc = -ENOMEM; - goto unlock; - } - } /* * If firmware name changed, frees firmware. As free_firmware will @@ -1426,10 +1416,15 @@ static int xc2028_set_config(struct dvb_frontend *fe, void *priv_cfg) if (priv->state == XC2028_NO_FIRMWARE) { if (!firmware_name[0]) - priv->fname = priv->ctrl.fname; + priv->fname = kstrdup(p->fname, GFP_KERNEL); else priv->fname = firmware_name; + if (!priv->fname) { + rc = -ENOMEM; + goto unlock; + } + rc = request_firmware_nowait(THIS_MODULE, 1, priv->fname, priv->i2c_props.adap->dev.parent, |