Re: [syzbot] [block?] WARNING in blk_mq_free_tag_set

[syzbot <syzbot+02b37e31e64ea5cb6d29@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    a8406e6c0b79 Add linux-next specific files for 20260825
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=114f1625580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=da8932b2925a9804
dashboard link: https://syzkaller.appspot.com/bug?extid=02b37e31e64ea5cb6d29
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13dad979580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10136979580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bd019bacac75/disk-a8406e6c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e47580ccc38d/vmlinux-a8406e6c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b7909a5638c6/bzImage-a8406e6c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+02b37e31e64ea5cb6d29@syzkaller.appspotmail.com

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timer_delete_sync(&sdp->delay_work) && rcu_segcblist_n_cbs(&sdp->srcu_cblist)
WARNING: kernel/rcu/srcutree.c:707 at cleanup_srcu_struct+0x3d6/0x8b0 kernel/rcu/srcutree.c:706, CPU#0: syz.0.1231/9288
Modules linked in:
CPU: 0 UID: 0 PID: 9288 Comm: syz.0.1231 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:cleanup_srcu_struct+0x3d6/0x8b0 kernel/rcu/srcutree.c:706
Code: f3 8b 00 48 83 7d 00 00 4c 8b 74 24 10 0f 85 dd 03 00 00 41 ff c5 41 83 e5 0f 41 83 fd 07 0f 86 e2 fe ff ff e9 ab 00 00 00 90 <0f> 0b 90 4c 8d b5 00 02 00 00 4c 89 f3 48 c1 eb 03 48 b8 00 00 00
RSP: 0018:ffffc900033c7cf0 EFLAGS: 00010206
RAX: 1ffffd1ffff81745 RBX: 0000607edaf36940 RCX: dffffc0000000000
RDX: 0000000000000001 RSI: ffffffff8e478a87 RDI: 00000000ffffffff
RBP: ffffe8ffffc0b940 R08: ffffffff907a4f7f R09: 1ffffffff20f49ef
R10: dffffc0000000000 R11: fffffbfff20f49f0 R12: ffff888054a1e800
R13: 0000000000000000 R14: ffffe8ffffc0ba28 R15: 1ffffffff1ce95de
FS:  00007f73abf2d6c0(0000) GS:ffff888124cd5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000100 CR3: 0000000076d8a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 blk_mq_free_tag_set+0x617/0x790 block/blk-mq.c:4976
 loop_remove+0x4e/0xc0 drivers/block/loop.c:2143
 loop_control_remove drivers/block/loop.c:2201 [inline]
 loop_control_ioctl+0x4a6/0x5a0 drivers/block/loop.c:2243
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f73aaf9e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f73abf2d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f73ab225fa0 RCX: 00007f73aaf9e0d9
RDX: 0000000000000001 RSI: 0000000000004c81 RDI: 0000000000000003
RBP: 00007f73ab035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f73ab226038 R14: 00007f73ab225fa0 R15: 00007ffe4f51e5e8
 </TASK>


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