On 4/15/21 8:07 AM, Igor Matheus Andrade Torrente wrote:
Fixes a race condition - for lack of a more precise term - between
em28xx_v4l2_open and em28xx_v4l2_init, by detaching the v4l2_dev,
media_pad and vdev structs from the em28xx_v4l2, and managing the
lifetime of those objects more dynamicaly.
The race happens when a thread[1] - containing the em28xx_v4l2_init()
code - calls the v4l2_mc_create_media_graph(), and it return a error,
if a thread[2] - running v4l2_open() - pass the verification point
and reaches the em28xx_v4l2_open() before the thread[1] finishes
the deregistration of v4l2 subsystem, the thread[1] will free all
resources before the em28xx_v4l2_open() can process their things,
because the em28xx_v4l2_init() has the dev->lock. And all this lead
the thread[2] to cause a user-after-free.
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-and-tested-by: syzbot+b2391895514ed9ef4a8e@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Igor Matheus Andrade Torrente <igormtorrente@xxxxxxxxx>
---
V2: Add v4l2_i2c_new_subdev null check
Deal with v4l2 subdevs dependencies
V3: Fix link error when compiled as a module
---
drivers/media/usb/em28xx/em28xx-camera.c | 4 +-
drivers/media/usb/em28xx/em28xx-video.c | 300 +++++++++++++++--------
drivers/media/usb/em28xx/em28xx.h | 6 +-
3 files changed, 209 insertions(+), 101 deletions(-)
The changes looks good to me. Have you tried building as a modules and
running modprobes and rmmods? You can do that without a device.
thanks,
-- Shuah
