Messages in this thread | | | Subject | Re: [PATCH RFC v3] media: em28xx: Fix race condition between open and init function | From | Shuah Khan <> | Date | Fri, 16 Apr 2021 17:03:05 -0600 |
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On 4/16/21 1:33 PM, Igor Torrente wrote: > > > On 4/15/21 2:25 PM, Shuah Khan wrote: >> 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@intel.com> >>> Reported-and-tested-by: >>> syzbot+b2391895514ed9ef4a8e@syzkaller.appspotmail.com >>> Signed-off-by: Igor Matheus Andrade Torrente <igormtorrente@gmail.com> >>> --- >>> >>> 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. >> > > I tried and everything worked fine. >
Thank you.
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
thanks, -- Shuah
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