Re: general protection fault in vb2_mmap

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    442b8cea2477 Add linux-next specific files for 20181109
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15c7654d400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2f72bdb11df9fbe8
dashboard link: https://syzkaller.appspot.com/bug?extid=52e5bf0ebfa66092937a
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1492dfbd400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16d6e6d5400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+52e5bf0ebfa66092937a@xxxxxxxxxxxxxxxxxxxxxxxxx

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 6333 Comm: syz-executor804 Not tainted  
4.20.0-rc1-next-20181109+ #110
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__find_plane_by_offset  
drivers/media/common/videobuf2/videobuf2-core.c:2006 [inline]
RIP: 0010:vb2_mmap+0x23c/0x6f0  
drivers/media/common/videobuf2/videobuf2-core.c:2128
Code: 80 3c 10 00 0f 85 1b 04 00 00 48 b9 00 00 00 00 00 fc ff df 48 8b 45  
b8 48 8b 00 48 8d 78 14 48 89 45 d0 48 89 f8 48 c1 e8 03 <0f> b6 14 08 48  
89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 fa
RSP: 0018:ffff8801c111f7d0 EFLAGS: 00010203
RAX: 0000000000000002 RBX: 000000000000000a RCX: dffffc0000000000
RDX: dffffc0000000000 RSI: ffffffff854c01c0 RDI: 0000000000000014
RBP: ffff8801c111f820 R08: ffff8801c23e8400 R09: ffffed0039c39966
R10: ffffed0039c39966 R11: ffff8801ce1ccb37 R12: 0000000000000000
R13: 0000000000000001 R14: 0000000020a00000 R15: ffff8801cb777268
FS:  00000000020b8880(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006cf090 CR3: 00000001b531c000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 vb2_fop_mmap+0x4b/0x70 drivers/media/common/videobuf2/videobuf2-v4l2.c:999
 v4l2_mmap+0x153/0x200 drivers/media/v4l2-core/v4l2-dev.c:401
 call_mmap include/linux/fs.h:1872 [inline]
 mmap_region+0xe85/0x1cd0 mm/mmap.c:1786
 do_mmap+0xa22/0x1230 mm/mmap.c:1559
 do_mmap_pgoff include/linux/mm.h:2328 [inline]
 vm_mmap_pgoff+0x213/0x2c0 mm/util.c:350
 ksys_mmap_pgoff+0x4da/0x660 mm/mmap.c:1609
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
 __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x444c09
Code: e8 ac e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 2b ce fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff3df375f8 EFLAGS: 00000212 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000444c09
RDX: 00000000ffffffff RSI: 0000000000600000 RDI: 0000000020a00000
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000020a00000
R10: 0000000000000011 R11: 0000000000000212 R12: 000000000000977e
R13: 0000000000401f50 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace eab0c06c6f6dccfa ]---
RIP: 0010:__find_plane_by_offset  
drivers/media/common/videobuf2/videobuf2-core.c:2006 [inline]
RIP: 0010:vb2_mmap+0x23c/0x6f0  
drivers/media/common/videobuf2/videobuf2-core.c:2128
Code: 80 3c 10 00 0f 85 1b 04 00 00 48 b9 00 00 00 00 00 fc ff df 48 8b 45  
b8 48 8b 00 48 8d 78 14 48 89 45 d0 48 89 f8 48 c1 e8 03 <0f> b6 14 08 48  
89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 fa
RSP: 0018:ffff8801c111f7d0 EFLAGS: 00010203
RAX: 0000000000000002 RBX: 000000000000000a RCX: dffffc0000000000
RDX: dffffc0000000000 RSI: ffffffff854c01c0 RDI: 0000000000000014
RBP: ffff8801c111f820 R08: ffff8801c23e8400 R09: ffffed0039c39966
R10: ffffed0039c39966 R11: ffff8801ce1ccb37 R12: 0000000000000000
R13: 0000000000000001 R14: 0000000020a00000 R15: ffff8801cb777268
FS:  00000000020b8880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000414ca0 CR3: 00000001b531c000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400