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authorTakashi Iwai <tiwai@suse.de>2016-11-17 10:49:31 +0100
committerMauro Carvalho Chehab <mchehab@s-opensource.com>2016-11-23 21:04:26 -0200
commit22a1e7783e173ab3d86018eb590107d68df46c11 (patch)
tree3beaea52d877cfab058a52b97a2e2f4d6f170b4e
parent9c763584b7c8911106bb77af7e648bef09af9d80 (diff)
xc2028: Fix use-after-free bug properlymedia/v4.9-4
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.c37
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,

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