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media: saa7134: fix use after free bug in saa7134_finidev due to race condition

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In saa7134_initdev, it will call saa7134_hwinit1. There are three
function invoking here: saa7134_video_init1, saa7134_ts_init1
and saa7134_vbi_init1.

All of them will init a timer with same function. Take
saa7134_video_init1 as an example. It'll bound &dev->video_q.timeout
with saa7134_buffer_timeout.

In buffer_activate, the timer funtcion is started.

If we remove the module or device which will call saa7134_finidev
to make cleanup, there may be a unfinished work. The
possible sequence is as follows, which will cause a
typical UAF bug.

Fix it by canceling the timer works accordingly before cleanup in
saa7134_finidev.

CPU0                  CPU1

                    |saa7134_buffer_timeout
saa7134_finidev     |
  kfree(dev);       |
                    |
                    | saa7134_buffer_next
                    | //use dev

Fixes: 1e7126b4a8 ("media: saa7134: Convert timers to use timer_setup()")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
This commit is contained in:
Zheng Wang 2023-03-18 16:50:23 +08:00 committed by Hans Verkuil
parent 5abda7a166
commit 30cf57da17
3 changed files with 3 additions and 0 deletions
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1
drivers/media/pci/saa7134/saa7134-ts.c
View File

@ -300,6 +300,7 @@ int saa7134_ts_start(struct saa7134_dev *dev)
int saa7134_ts_fini(struct saa7134_dev *dev)
{
del_timer_sync(&dev->ts_q.timeout);
saa7134_pgtable_free(dev->pci, &dev->ts_q.pt);
return 0;
}

1
drivers/media/pci/saa7134/saa7134-vbi.c
View File

@ -185,6 +185,7 @@ int saa7134_vbi_init1(struct saa7134_dev *dev)
int saa7134_vbi_fini(struct saa7134_dev *dev)
{
/* nothing */
del_timer_sync(&dev->vbi_q.timeout);
return 0;
}

1
drivers/media/pci/saa7134/saa7134-video.c
View File

@ -1743,6 +1743,7 @@ int saa7134_video_init1(struct saa7134_dev *dev)
void saa7134_video_fini(struct saa7134_dev *dev)
{
del_timer_sync(&dev->video_q.timeout);
/* free stuff */
saa7134_pgtable_free(dev->pci, &dev->video_q.pt);
saa7134_pgtable_free(dev->pci, &dev->vbi_q.pt);