[syzbot] WARNING in inc_nlink (2)

[syzbot <syzbot+1c8034b9f0e640f9ba45@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    57fbdb15 Merge tag 'scsi-fixes' of git://git.kernel.org/pu..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11e2ccfcd00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=71a75beb62b62a34
dashboard link: https://syzkaller.appspot.com/bug?extid=1c8034b9f0e640f9ba45
compiler:       Debian clang version 11.0.1-2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11bfd511d00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17ff8c5ed00000

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12b82fbed00000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=11b82fbed00000
console output: https://syzkaller.appspot.com/x/log.txt?x=16b82fbed00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1c8034b9f0e640f9ba45@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 4
VFS: Found a V7 FS (block size = 512) on device loop0
------------[ cut here ]------------
WARNING: CPU: 1 PID: 8352 at fs/inode.c:362 inc_nlink+0x11e/0x130 fs/inode.c:362
Modules linked in:
CPU: 1 PID: 8352 Comm: syz-executor549 Not tainted 5.12.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:inc_nlink+0x11e/0x130 fs/inode.c:362
Code: ef ff e9 38 ff ff ff 44 89 e9 80 e1 07 80 c1 03 38 c1 0f 8c 49 ff ff ff 4c 89 ef e8 fc 3f ef ff e9 3c ff ff ff e8 42 59 ab ff <0f> 0b eb 80 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 41 57 41 56
RSP: 0018:ffffc9000178fdf8 EFLAGS: 00010293
RAX: ffffffff81cdbf6e RBX: 1ffff110064a6810 RCX: ffff888015279c40
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff81cdbee8 R09: ffffc9000178fdc8
R10: fffff520002f1fbd R11: 0000000000000000 R12: dffffc0000000000
R13: ffff888032534080 R14: ffff888032534038 R15: 0000000000000000
FS:  0000000000ba9300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb76c03c0e8 CR3: 0000000011cf3000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 inode_inc_link_count include/linux/fs.h:2297 [inline]
 sysv_mkdir+0x1d/0x120 fs/sysv/namei.c:119
 vfs_mkdir+0x45b/0x640 fs/namei.c:3817
 do_mkdirat+0x209/0x370 fs/namei.c:3842
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x443c29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff53c97208 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00000000004004a0 RCX: 0000000000443c29
RDX: 00000000004021f3 RSI: 0000000000000023 RDI: 0000000020000080
RBP: 00000000004034c0 R08: 0000000000000000 R09: 0000000000000000
R10: 00007fff53c970d0 R11: 0000000000000246 R12: 0000000000403550
R13: 0000000000000000 R14: 00000000004b1018 R15: 00000000004004a0


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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches