BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
IP: refcount_dec_and_test arch/x86/include/asm/refcount.h:75 [inline]
IP: vb2_vmalloc_put+0x9/0x60 drivers/media/v4l2-core/videobuf2-vmalloc.c:68
PGD a75d9067 P4D a75d9067 PUD 5b026067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 31314 Comm: syz-executor.0 Not tainted 4.14.292-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
task: ffff8880616ee040 task.stack: ffff888093570000
RIP: 0010:refcount_dec_and_test arch/x86/include/asm/refcount.h:75 [inline]
RIP: 0010:vb2_vmalloc_put+0x9/0x60 drivers/media/v4l2-core/videobuf2-vmalloc.c:68
RSP: 0018:ffff888093577900 EFLAGS: 00010246
RAX: 0000000000040000 RBX: ffff8880aac38540 RCX: ffffc90007ff4000
RDX: 0000000000040000 RSI: ffffffff84c20ac9 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8880aac38554 R14: 0000000000000000 R15: ffffffff84c20ac0
FS:  00007f559a27b700(0000) GS:ffff8880ba400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000020 CR3: 0000000059dda000 CR4: 00000000003406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __vb2_buf_mem_free+0xfa/0x1d0 drivers/media/v4l2-core/videobuf2-core.c:240
 __vb2_free_mem drivers/media/v4l2-core/videobuf2-core.c:409 [inline]
 __vb2_queue_free+0x60d/0x7a0 drivers/media/v4l2-core/videobuf2-core.c:454
 vb2_core_reqbufs+0x1cc/0x910 drivers/media/v4l2-core/videobuf2-core.c:687
 vb2_ioctl_reqbufs+0x1b6/0x320 drivers/media/v4l2-core/videobuf2-v4l2.c:718
 v4l_reqbufs drivers/media/v4l2-core/v4l2-ioctl.c:1863 [inline]
 v4l_reqbufs+0x98/0xc0 drivers/media/v4l2-core/v4l2-ioctl.c:1852
 __video_do_ioctl+0x65b/0x6a0 drivers/media/v4l2-core/v4l2-ioctl.c:2738
 video_usercopy+0xfd/0xe70 drivers/media/v4l2-core/v4l2-ioctl.c:2908
 v4l2_ioctl+0x1bb/0x2f0 drivers/media/v4l2-core/v4l2-dev.c:360
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f559b948409
RSP: 002b:00007f559a27b168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f559ba5b120 RCX: 00007f559b948409
RDX: 00000000200001c0 RSI: 00000000c0145608 RDI: 0000000000000003
RBP: 00007f559b9a3367 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe3656eeff R14: 00007f559a27b300 R15: 0000000000022000
Code: e9 ca fc ff ff e8 88 f3 bc fc e9 96 fc ff ff e8 ae f5 bc fc e9 fd fe ff ff 66 0f 1f 84 00 00 00 00 00 55 48 89 fd e8 f7 3c 93 fc <f0> ff 4d 20 0f 88 3d c3 5f 02 74 06 5d e9 e5 3c 93 fc e8 e0 3c 
RIP: refcount_dec_and_test arch/x86/include/asm/refcount.h:75 [inline] RSP: ffff888093577900
RIP: vb2_vmalloc_put+0x9/0x60 drivers/media/v4l2-core/videobuf2-vmalloc.c:68 RSP: ffff888093577900
CR2: 0000000000000020
---[ end trace 4b24e1580361d411 ]---
----------------
Code disassembly (best guess):
   0:	e9 ca fc ff ff       	jmpq   0xfffffccf
   5:	e8 88 f3 bc fc       	callq  0xfcbcf392
   a:	e9 96 fc ff ff       	jmpq   0xfffffca5
   f:	e8 ae f5 bc fc       	callq  0xfcbcf5c2
  14:	e9 fd fe ff ff       	jmpq   0xffffff16
  19:	66 0f 1f 84 00 00 00 	nopw   0x0(%rax,%rax,1)
  20:	00 00
  22:	55                   	push   %rbp
  23:	48 89 fd             	mov    %rdi,%rbp
  26:	e8 f7 3c 93 fc       	callq  0xfc933d22
* 2b:	f0 ff 4d 20          	lock decl 0x20(%rbp) <-- trapping instruction
  2f:	0f 88 3d c3 5f 02    	js     0x25fc372
  35:	74 06                	je     0x3d
  37:	5d                   	pop    %rbp
  38:	e9 e5 3c 93 fc       	jmpq   0xfc933d22
  3d:	e8                   	.byte 0xe8
  3e:	e0 3c                	loopne 0x7c