Hello,
syzbot has tested the proposed patch but the reproducer still triggered
crash:
possible deadlock in vidioc_querycap
============================================
WARNING: possible recursive locking detected
5.3.0-rc7+ #0 Not tainted
--------------------------------------------
v4l_id/3016 is trying to acquire lock:
0000000069c3004e (&usbvision->v4l2_lock){+.+.}, at:
vidioc_querycap+0x62/0x3b0 drivers/media/usb/usbvision/usbvision-video.c:456
but task is already holding lock:
0000000069c3004e (&usbvision->v4l2_lock){+.+.}, at:
__video_do_ioctl+0x3ba/0xba0 drivers/media/v4l2-core/v4l2-ioctl.c:2846
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&usbvision->v4l2_lock);
lock(&usbvision->v4l2_lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
1 lock held by v4l_id/3016:
#0: 0000000069c3004e (&usbvision->v4l2_lock){+.+.}, at:
__video_do_ioctl+0x3ba/0xba0 drivers/media/v4l2-core/v4l2-ioctl.c:2846
stack backtrace:
CPU: 0 PID: 3016 Comm: v4l_id Not tainted 5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0xca/0x13e lib/dump_stack.c:113
print_deadlock_bug kernel/locking/lockdep.c:2301 [inline]
check_deadlock kernel/locking/lockdep.c:2342 [inline]
validate_chain kernel/locking/lockdep.c:2881 [inline]
__lock_acquire.cold+0x148/0x29b kernel/locking/lockdep.c:3880
lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4412
__mutex_lock_common kernel/locking/mutex.c:930 [inline]
__mutex_lock+0x158/0x1360 kernel/locking/mutex.c:1077
vidioc_querycap+0x62/0x3b0
drivers/media/usb/usbvision/usbvision-video.c:456
v4l_querycap+0x121/0x340 drivers/media/v4l2-core/v4l2-ioctl.c:1058
__video_do_ioctl+0x969/0xba0 drivers/media/v4l2-core/v4l2-ioctl.c:2878
video_usercopy+0x446/0xf40 drivers/media/v4l2-core/v4l2-ioctl.c:3060
v4l2_ioctl+0x1a2/0x220 drivers/media/v4l2-core/v4l2-dev.c:360
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0xd2d/0x1330 fs/ioctl.c:696
ksys_ioctl+0x9b/0xc0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:718
do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f642b0b9347
Code: 90 90 90 48 8b 05 f1 fa 2a 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff
ff c3 90 90 90 90 90 90 90 90 90 90 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff
ff 73 01 c3 48 8b 0d c1 fa 2a 00 31 d2 48 29 c2 64
RSP: 002b:00007ffc2fc62b28 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f642b0b9347
RDX: 00007ffc2fc62b30 RSI: 0000000080685600 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000400884
R13: 00007ffc2fc62c80 R14: 0000000000000000 R15: 0000000000000000
Tested on:
commit: f0df5c1b usb-fuzzer: main usb gadget fuzzer driver
git tree: https://github.com/google/kasan.git
console output: https://syzkaller.appspot.com/x/log.txt?x=160d95c3600000
kernel config: https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
dashboard link: https://syzkaller.appspot.com/bug?extid=7fa38a608b1075dfd634
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
patch: https://syzkaller.appspot.com/x/patch.diff?x=125290b1600000
