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media: pvrusb2: fix use after free on context disconnection

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Upon module load, a kthread is created targeting the
pvr2_context_thread_func function, which may call pvr2_context_destroy
and thus call kfree() on the context object. However, that might happen
before the usb hub_event handler is able to notify the driver. This
patch adds a sanity check before the invalid read reported by syzbot,
within the context disconnection call stack.

Reported-and-tested-by: syzbot+621409285c4156a009b3@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/000000000000a02a4205fff8eb92@google.com/

Fixes: e5be15c638 ("V4L/DVB (7711): pvrusb2: Fix race on module unload")
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Acked-by: Mike Isely <isely@pobox.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
This commit is contained in:
Ricardo B. Marliere 2023-10-13 01:09:12 +02:00 committed by Mauro Carvalho Chehab
parent 0cb8c94825
commit ded85b0c0e
1 changed files with 2 additions and 1 deletions
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3
drivers/media/usb/pvrusb2/pvrusb2-context.c
View file

@ -268,7 +268,8 @@ void pvr2_context_disconnect(struct pvr2_context *mp)
{
pvr2_hdw_disconnect(mp->hdw);
mp->disconnect_flag = !0;
pvr2_context_notify(mp);
if (!pvr2_context_shutok())
pvr2_context_notify(mp);
}