linux-kernel - Re: [syzbot] [fuse?] WARNING: refcount bug in process_scheduled

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Message-ID: <6889ee8c.a00a0220.26d0e1.001a.GAE@google.com>
Date: Wed, 30 Jul 2025 03:06:04 -0700
From: syzbot <syzbot+9921e319bd6168140b40@...kaller.appspotmail.com>
To: hdanton@...a.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [fuse?] WARNING: refcount bug in process_scheduled_works

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in mddev_put

------------[ cut here ]------------
kernel BUG at drivers/md/md.c:641!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 6690 Comm: syz.0.18 Not tainted 6.16.0-syzkaller-04405-g4b290aae788e-dirty #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:__mddev_put drivers/md/md.c:641 [inline]
RIP: 0010:mddev_put+0x1e9/0x1f0 drivers/md/md.c:660
Code: f9 e9 3f ff ff ff 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c 6d ff ff ff 4c 89 f7 e8 c2 ed e0 f9 e9 60 ff ff ff e8 f8 da 7e f9 90 <0f> 0b 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90002f27cb0 EFLAGS: 00010293
RAX: ffffffff8840e0e8 RBX: ffff888032332000 RCX: ffff88807b13da00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff888032332133 R09: 1ffff11006466426
R10: dffffc0000000000 R11: ffffed1006466427 R12: ffff88806364e000
R13: ffff888148c47310 R14: ffff888032332130 R15: dffffc0000000000
FS:  000055558e36e500(0000) GS:ffff888125c86000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000007 CR3: 000000005c370000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 bdev_release+0x536/0x650 block/bdev.c:-1
 blkdev_release+0x15/0x20 block/fops.c:699
 __fput+0x44c/0xa70 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xec/0x110 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:208 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9d1d58e9a9
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffee3402d38 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 0000000000025060 RCX: 00007f9d1d58e9a9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f9d1d7b7ba0 R08: 0000000000000001 R09: 00000008e340302f
R10: 00007f9d1d400000 R11: 0000000000000246 R12: 00007f9d1d7b5fac
R13: 00007f9d1d7b5fa0 R14: ffffffffffffffff R15: 00007ffee3402e50
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__mddev_put drivers/md/md.c:641 [inline]
RIP: 0010:mddev_put+0x1e9/0x1f0 drivers/md/md.c:660
Code: f9 e9 3f ff ff ff 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c 6d ff ff ff 4c 89 f7 e8 c2 ed e0 f9 e9 60 ff ff ff e8 f8 da 7e f9 90 <0f> 0b 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90002f27cb0 EFLAGS: 00010293
RAX: ffffffff8840e0e8 RBX: ffff888032332000 RCX: ffff88807b13da00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff888032332133 R09: 1ffff11006466426
R10: dffffc0000000000 R11: ffffed1006466427 R12: ffff88806364e000
R13: ffff888148c47310 R14: ffff888032332130 R15: dffffc0000000000
FS:  000055558e36e500(0000) GS:ffff888125c86000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000007 CR3: 000000005c370000 CR4: 0000000000350ef0


Tested on:

commit:         4b290aae Merge tag 'sysctl-6.17-rc1' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11948834580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dea300d7050f7861
dashboard link: https://syzkaller.appspot.com/bug?extid=9921e319bd6168140b40
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1394ccf0580000