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| author | Abhishek Kumar <abhishek_sts8@yahoo.com> | 2026-03-10 22:14:37 +0530 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-04-22 13:30:51 +0200 |
| commit | 6b9e66437cc6123ddedac141e1b8b6fcf57d2972 (patch) | |
| tree | 50c8d5c2357df2f76d6618ccd158aa20f64bd79b | |
| parent | 93d9a58961a9e09306857e999b3ee76aa4be67f0 (diff) | |
| download | linux-stable-6b9e66437cc6123ddedac141e1b8b6fcf57d2972.tar.gz linux-stable-6b9e66437cc6123ddedac141e1b8b6fcf57d2972.zip | |
media: em28xx: fix use-after-free in em28xx_v4l2_open()
commit a66485a934c7187ae8e36517d40615fa2e961cff upstream.
em28xx_v4l2_open() reads dev->v4l2 without holding dev->lock,
creating a race with em28xx_v4l2_init()'s error path and
em28xx_v4l2_fini(), both of which free the em28xx_v4l2 struct
and set dev->v4l2 to NULL under dev->lock.
This race leads to two issues:
- use-after-free in v4l2_fh_init() when accessing vdev->ctrl_handler,
since the video_device is embedded in the freed em28xx_v4l2 struct.
- NULL pointer dereference in em28xx_resolution_set() when accessing
v4l2->norm, since dev->v4l2 has been set to NULL.
Fix this by moving the mutex_lock() before the dev->v4l2 read and
adding a NULL check for dev->v4l2 under the lock.
Reported-by: syzbot+c025d34b8eaa54c571b8@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c025d34b8eaa54c571b8
Fixes: 8139a4d583ab ("[media] em28xx: move v4l2 user counting fields from struct em28xx to struct v4l2")
Cc: stable@vger.kernel.org
Signed-off-by: Abhishek Kumar <abhishek_sts8@yahoo.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/media/usb/em28xx/em28xx-video.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c index 2dfa3242a7ab..14c35995cd95 100644 --- a/drivers/media/usb/em28xx/em28xx-video.c +++ b/drivers/media/usb/em28xx/em28xx-video.c @@ -2126,7 +2126,7 @@ static int em28xx_v4l2_open(struct file *filp) { struct video_device *vdev = video_devdata(filp); struct em28xx *dev = video_drvdata(filp); - struct em28xx_v4l2 *v4l2 = dev->v4l2; + struct em28xx_v4l2 *v4l2; enum v4l2_buf_type fh_type = 0; int ret; @@ -2143,13 +2143,19 @@ static int em28xx_v4l2_open(struct file *filp) return -EINVAL; } + if (mutex_lock_interruptible(&dev->lock)) + return -ERESTARTSYS; + + v4l2 = dev->v4l2; + if (!v4l2) { + mutex_unlock(&dev->lock); + return -ENODEV; + } + em28xx_videodbg("open dev=%s type=%s users=%d\n", video_device_node_name(vdev), v4l2_type_names[fh_type], v4l2->users); - if (mutex_lock_interruptible(&dev->lock)) - return -ERESTARTSYS; - ret = v4l2_fh_open(filp); if (ret) { dev_err(&dev->intf->dev, |