WARNING in dma_buf_vunmap

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 58b454eb Linux 4.14.112
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15fe7dfd200000
kernel config: https://syzkaller.appspot.com/x/.config?x=8b0e7ab7678533ab
dashboard link: https://syzkaller.appspot.com/bug?extid=9f85443bf7419f90494c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13a95ca0a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13677680a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9f8544...@syzkaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
audit: type=1400 audit(1555510482.116:36): avc: denied { map } for
pid=7145 comm="syz-executor348" path="/root/syz-executor348569542"
dev="sda1" ino=16483 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
------------[ cut here ]------------
WARNING: CPU: 0 PID: 7145 at drivers/dma-buf/dma-buf.c:1039
dma_buf_vunmap+0x18f/0x200 drivers/dma-buf/dma-buf.c:1039
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 7145 Comm: syz-executor348 Not tainted 4.14.112 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x138/0x19c lib/dump_stack.c:53
panic+0x1f2/0x438 kernel/panic.c:182
__warn.cold+0x2f/0x34 kernel/panic.c:546
report_bug+0x216/0x254 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:177 [inline]
fixup_bug arch/x86/kernel/traps.c:172 [inline]
do_error_trap+0x1bb/0x310 arch/x86/kernel/traps.c:295
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:944
RIP: 0010:dma_buf_vunmap+0x18f/0x200 drivers/dma-buf/dma-buf.c:1039
RSP: 0018:ffff8880939bfa88 EFLAGS: 00010297
RAX: ffff8880a57f8340 RBX: 0000000000000000 RCX: 1ffff11013e66ca7
RDX: 0000000000000000 RSI: ffffc90005daf000 RDI: 0000000000000000
RBP: ffff8880939bfab0 R08: dffffc0000000000 R09: ffffffff88c839e8
R10: ffff8880939bfba0 R11: ffff8880a57f8340 R12: ffffc90005daf000
R13: ffffc90005daf000 R14: ffff888090de4ca8 R15: ffff888089352c00
vb2_vmalloc_detach_dmabuf+0x5e/0x90
drivers/media/v4l2-core/videobuf2-vmalloc.c:407
__vb2_plane_dmabuf_put.isra.0+0x10f/0x300
drivers/media/v4l2-core/videobuf2-core.c:273
__vb2_buf_dmabuf_put drivers/media/v4l2-core/videobuf2-core.c:289 [inline]
__vb2_free_mem drivers/media/v4l2-core/videobuf2-core.c:411 [inline]
__vb2_queue_free+0x610/0x7e0 drivers/media/v4l2-core/videobuf2-core.c:454
vb2_core_queue_release+0x64/0x80
drivers/media/v4l2-core/videobuf2-core.c:2043
vb2_queue_release drivers/media/v4l2-core/videobuf2-v4l2.c:669 [inline]
_vb2_fop_release+0x1cf/0x2a0 drivers/media/v4l2-core/videobuf2-v4l2.c:840
vb2_fop_release+0x75/0xc0 drivers/media/v4l2-core/videobuf2-v4l2.c:854
vivid_fop_release+0x180/0x3f0 drivers/media/platform/vivid/vivid-core.c:486
v4l2_release+0xfb/0x190 drivers/media/v4l2-core/v4l2-dev.c:446
__fput+0x277/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x119/0x190 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x7df/0x2c10 kernel/exit.c:874
do_group_exit+0x111/0x330 kernel/exit.c:977
SYSC_exit_group kernel/exit.c:988 [inline]
SyS_exit_group+0x1d/0x20 kernel/exit.c:986
do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x442ba8
RSP: 002b:00007ffcf2d5cc58 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000442ba8
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004c2588 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d4180 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


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