WARNING in drop_nlink

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: af1af6ebca0e Linux 4.14.274
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16f246e7700000
kernel config: https://syzkaller.appspot.com/x/.config?x=425e8e4e86f35eba
dashboard link: https://syzkaller.appspot.com/bug?extid=35aa05baf75d3198e7cb
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+35aa05...@syzkaller.appspotmail.com

audit: type=1804 audit(1648630826.129:6): pid=10888 uid=0 auid=4294967295 ses=4294967295 op="invalid_pcr" cause="open_writers" comm="syz-executor.4" name="/root/syzkaller-testdir666728186/syzkaller.0DAu6U/95/bus/bus/file0" dev="sda1" ino=14067 res=1
------------[ cut here ]------------
WARNING: CPU: 0 PID: 10888 at fs/inode.c:285 drop_nlink+0x7d/0xd0 fs/inode.c:285
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 10888 Comm: syz-executor.4 Not tainted 4.14.274-syzkaller #0
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+0x1b2/0x281 lib/dump_stack.c:58
panic+0x1f9/0x42d kernel/panic.c:183
__warn.cold+0x20/0x44 kernel/panic.c:547
report_bug+0x208/0x250 lib/bug.c:183
fixup_bug arch/x86/kernel/traps.c:177 [inline]
fixup_bug arch/x86/kernel/traps.c:172 [inline]
do_error_trap+0x195/0x2d0 arch/x86/kernel/traps.c:295
invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:964
RIP: 0010:drop_nlink+0x7d/0xd0 fs/inode.c:285
RSP: 0018:ffff88809dbffce8 EFLAGS: 00010212
RAX: 0000000000040000 RBX: ffff88804a7a50a0 RCX: ffffc90008ff0000
RDX: 000000000000f332 RSI: ffffffff818c8d5d RDI: ffff88804a7a50a0
RBP: 00000000ffffffff R08: ffff8880b298a600 R09: dffffc0000000000
R10: 0000000000000000 R11: ffff8880b298a600 R12: ffff88804a7a50e8
R13: ffff88808e048600 R14: 0000000000000000 R15: 1ffff11013b7ffa9
ovl_do_remove+0x5d6/0xb90 fs/overlayfs/dir.c:781
vfs_unlink+0x230/0x470 fs/namei.c:4027
do_unlinkat+0x30c/0x5c0 fs/namei.c:4092
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f8f0286c049
RSP: 002b:00007f8f011e1168 EFLAGS: 00000246 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 00007f8f0297ef60 RCX: 00007f8f0286c049
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000540
RBP: 00007f8f028c608d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffff903261f R14: 00007f8f011e1300 R15: 0000000000022000
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: af1af6ebca0e Linux 4.14.274
git tree: linux-4.14.y

console output: https://syzkaller.appspot.com/x/log.txt?x=1039fe9b700000

kernel config: https://syzkaller.appspot.com/x/.config?x=425e8e4e86f35eba
dashboard link: https://syzkaller.appspot.com/bug?extid=35aa05baf75d3198e7cb
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10dee3e3700000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16c3902d700000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+35aa05...@syzkaller.appspotmail.com

overlayfs: fs on './file0' does not support file handles, falling back to index=off.
audit: type=1804 audit(1648632183.446:2): pid=7964 uid=0 auid=4294967295 ses=4294967295 op="invalid_pcr" cause="open_writers" comm="syz-executor238" name="/root/bus/bus/file0" dev="sda1" ino=13864 res=1
------------[ cut here ]------------
WARNING: CPU: 0 PID: 7964 at fs/inode.c:285 drop_nlink+0x7d/0xd0 fs/inode.c:285

Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 7964 Comm: syz-executor238 Not tainted 4.14.274-syzkaller #0

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+0x1b2/0x281 lib/dump_stack.c:58
panic+0x1f9/0x42d kernel/panic.c:183
__warn.cold+0x20/0x44 kernel/panic.c:547
report_bug+0x208/0x250 lib/bug.c:183
fixup_bug arch/x86/kernel/traps.c:177 [inline]
fixup_bug arch/x86/kernel/traps.c:172 [inline]
do_error_trap+0x195/0x2d0 arch/x86/kernel/traps.c:295
invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:964
RIP: 0010:drop_nlink+0x7d/0xd0 fs/inode.c:285

RSP: 0018:ffff88808dac7ce8 EFLAGS: 00010297
RAX: ffff8880964c45c0 RBX: ffff8880976310a0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880976310a0
RBP: 00000000ffffffff R08: ffff8880964c45c0 R09: dffffc0000000000
R10: 0000000000000000 R11: ffff8880964c45c0 R12: ffff8880976310e8
R13: ffff88808e4e0580 R14: 0000000000000000 R15: 1ffff11011b58fa9

ovl_do_remove+0x5d6/0xb90 fs/overlayfs/dir.c:781
vfs_unlink+0x230/0x470 fs/namei.c:4027
do_unlinkat+0x30c/0x5c0 fs/namei.c:4092
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

RIP: 0033:0x7f1f6ef6af99
RSP: 002b:00007ffd74fb74e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 00007ffd74fb74f8 RCX: 00007f1f6ef6af99
RDX: 00007f1f6ef6af99 RSI: bf4714f75c52275c RDI: 0000000020000540
RBP: 00007ffd74fb74f0 R08: 00007f1f6ef294f0 R09: 00007f1f6ef294f0
R10: 00007f1f6ef294f0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000