Re: [PATCH usb] media/pvrusb2: fix uaf in pvr2_context_set_notify

[Greg KH]

On Fri, Feb 16, 2024 at 03:30:47PM +0800, Edward Adam Davis wrote:
> [Syzbot reported]
> BUG: KASAN: slab-use-after-free in pvr2_context_set_notify+0x2c4/0x310 drivers/media/usb/pvrusb2/pvrusb2-context.c:35
> Read of size 4 at addr ffff888113aeb0d8 by task kworker/1:1/26
> 
> CPU: 1 PID: 26 Comm: kworker/1:1 Not tainted 6.8.0-rc1-syzkaller-00046-gf1a27f081c1f #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
> Workqueue: usb_hub_wq hub_event
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
>  print_address_description mm/kasan/report.c:377 [inline]
>  print_report+0xc4/0x620 mm/kasan/report.c:488
>  kasan_report+0xda/0x110 mm/kasan/report.c:601
>  pvr2_context_set_notify+0x2c4/0x310 drivers/media/usb/pvrusb2/pvrusb2-context.c:35
>  pvr2_context_notify drivers/media/usb/pvrusb2/pvrusb2-context.c:95 [inline]
>  pvr2_context_disconnect+0x94/0xb0 drivers/media/usb/pvrusb2/pvrusb2-context.c:272
> 
> Freed by task 906:
> kasan_save_stack+0x33/0x50 mm/kasan/common.c:47
> kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> kasan_save_free_info+0x3f/0x60 mm/kasan/generic.c:640
> poison_slab_object mm/kasan/common.c:241 [inline]
> __kasan_slab_free+0x106/0x1b0 mm/kasan/common.c:257
> kasan_slab_free include/linux/kasan.h:184 [inline]
> slab_free_hook mm/slub.c:2121 [inline]
> slab_free mm/slub.c:4299 [inline]
> kfree+0x105/0x340 mm/slub.c:4409
> pvr2_context_check drivers/media/usb/pvrusb2/pvrusb2-context.c:137 [inline]
> pvr2_context_thread_func+0x69d/0x960 drivers/media/usb/pvrusb2/pvrusb2-context.c:158
> 
> [Analyze]
> Task A set disconnect_flag = !0, which resulted in Task B's condition being met
> and releasing mp, leading to this issue.
> 
> [Fix]
> Place the disconnect_flag assignment operation after all code in pvr2_context_disconnect()
> to avoid this issue.
> 
> Reported-and-tested-by: syzbot+ce750e124675d4599449@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>

What commit id does this fix?

And should it be cc: stable as well?

thanks,

greg k-h