[syzbot] WARNING in futex_requeue

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b91db6a0b52e Merge tag 'for-5.15/io_uring-vfs-2021-08-30' ..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17907235300000
kernel config: https://syzkaller.appspot.com/x/.config?x=961d30359ac81f8c
dashboard link: https://syzkaller.appspot.com/bug?extid=4d1bd0725ef09168e1a0
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1222185d300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4d1bd0...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 5701 at kernel/futex.c:2259 futex_requeue+0x1467/0x2d50 kernel/futex.c:2259
Modules linked in:
CPU: 1 PID: 5701 Comm: syz-executor.0 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:futex_requeue+0x1467/0x2d50 kernel/futex.c:2259
Code: 02 00 00 4c 8d 84 24 90 02 00 00 e8 63 6a 00 00 41 89 c7 31 ff 89 c6 e8 a7 4d 0c 00 45 85 ff 0f 84 d8 13 00 00 e8 89 49 0c 00 <0f> 0b eb 05 e8 80 49 0c 00 4c 89 fb 89 df 48 c7 c6 70 7c 73 8c e8
RSP: 0018:ffffc90001d5f640 EFLAGS: 00010293
RAX: ffffffff8174a337 RBX: 0000000000000df3 RCX: ffff888020e7b880
RDX: 0000000000000000 RSI: 00000000fffffffd RDI: 0000000000000000
RBP: ffffc90001d5f948 R08: ffffffff8174a329 R09: ffffed1005174a9e
R10: ffffed1005174a9e R11: 0000000000000000 R12: 0000000020048000
R13: dffffc0000000000 R14: 0000000000000000 R15: 00000000fffffffd
FS: 00007f4d7080c700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd72dab690 CR3: 000000001cf4d000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
do_futex+0x1b87/0x32b0 kernel/futex.c:3958
__do_sys_futex kernel/futex.c:4009 [inline]
__se_sys_futex+0x11c/0x4d0 kernel/futex.c:3990
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665f9
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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4d7080c188 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 000000000056c038 RCX: 00000000004665f9
RDX: 0000000000000001 RSI: 000000000000000c RDI: 000000002000cffc
RBP: 00000000004bfcc4 R08: 0000000020048000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c038
R13: 00007fff6069004f R14: 00007f4d7080c300 R15: 0000000000022000


---
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[Thomas Gleixner]

On Wed, Sep 01 2021 at 06:26, syzbot wrote:
> syzbot found the following issue on:
>
> HEAD commit: b91db6a0b52e Merge tag 'for-5.15/io_uring-vfs-2021-08-30' ..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17907235300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=961d30359ac81f8c
> dashboard link: https://syzkaller.appspot.com/bug?extid=4d1bd0725ef09168e1a0
> compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1222185d300000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+4d1bd0...@syzkaller.appspotmail.com
>
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 5701 at kernel/futex.c:2259 futex_requeue+0x1467/0x2d50 kernel/futex.c:2259

Doh. That Gleixner dude did not think this through completely. Fix will
follow.

Thanks,

tglx