Messages in this thread | | | Subject | Re: [PATCH RFC v3] media: em28xx: Fix race condition between open and init function | From | Igor Torrente <> | Date | Fri, 16 Apr 2021 16:33:59 -0300 |
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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.
> thanks, > -- Shuah >
Thanks, --- Igor Matheus Andrade Torrente
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