WARNING in blk_mq_alloc_tag_set

Status: upstream: reported on 2026/07/28 12:58
Subsystems: block
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+18431bc7dccedc61778f@syzkaller.appspotmail.com
First crash: 50d, last: 18d
✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
4e7e770a repro-c Reproduced: ✅ WARNING in blk_mq_alloc_tag_set 2026/09/06 20:03 2026/09/06 20:03 2026/09/06 21:24 4f7b22a0
70962d8a repro-c 💥 WARNING in blk_mq_alloc_tag_set 2026/08/07 13:51 2026/08/07 17:09 2026/08/07 19:13 e4ef95d6
db396fa3 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ✅ WARNING in blk_mq_alloc_tag_set 2026/07/26 01:37 2026/07/26 01:37 2026/07/26 02:15 492bab15
Discussions (2)
Title Replies (including bot) Last reply
[syzbot] Monthly block report (Aug 2026) 0 (1) 2026/08/05 20:32
[syzbot] [block?] WARNING in blk_mq_alloc_tag_set 0 (1) 2026/07/28 12:58
Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/09/06 21:24 15m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 1fc5a74b108fc90951890ec513ac81869f5eaff1 report job log log

Sample crash report:
nvme nvme9: creating 2 I/O queues.
blk-mq: failed to allocate request map
------------[ cut here ]------------
timer_delete_sync(&sdp->delay_work) && rcu_segcblist_n_cbs(&sdp->srcu_cblist)
WARNING: kernel/rcu/srcutree.c:706 at cleanup_srcu_struct+0x6e4/0xb30 kernel/rcu/srcutree.c:706, CPU#1: syz.1.393/7000
Modules linked in:
CPU: 1 UID: 0 PID: 7000 Comm: syz.1.393 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
RIP: 0010:cleanup_srcu_struct+0x6e4/0xb30 kernel/rcu/srcutree.c:706
Code: 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 f4 03 00 00 48 8b 83 e8 00 00 00 48 8d 93 80 01 00 00 48 85 c0 0f 84 a7 fc ff ff 90 <0f> 0b 90 48 8d 8b 00 02 00 00 48 b8 00 00 00 00 00 fc ff df 48 89
RSP: 0018:ffffc90007faf9c8 EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffffe8ffffc7f000 RCX: ffffc90005b09000
RDX: ffffe8ffffc7f180 RSI: ffffffff81f5e92f RDI: ffff888030dacb00
RBP: ffff888067421800 R08: 0000000000000005 R09: 00000000ffffffff
R10: 0000000000000001 R11: 0000000000000000 R12: ffff8880540bc310
R13: 0000000000000000 R14: ffffffff8e6b00b0 R15: ffff8880540bc350
FS:  00007f8e73a846c0(0000) GS:ffff888123c79000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32821ff8 CR3: 000000002abe0000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 blk_mq_alloc_tag_set+0xdd8/0x1330 block/blk-mq.c:4928
 nvme_alloc_io_tag_set+0x3bc/0x750 drivers/nvme/host/core.c:5054
 nvme_loop_create_io_queues drivers/nvme/target/loop.c:515 [inline]
 nvme_loop_create_ctrl+0x6bc/0xee0 drivers/nvme/target/loop.c:610
 nvmf_create_ctrl drivers/nvme/host/fabrics.c:1359 [inline]
 nvmf_dev_write+0x4ee/0xb60 drivers/nvme/host/fabrics.c:1406
 vfs_write+0x2aa/0x1050 fs/read_write.c:685
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8e72b9e0d9
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:00007f8e73a84028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f8e72e25fa0 RCX: 00007f8e72b9e0d9
RDX: 000000000000001d RSI: 0000200000000800 RDI: 0000000000000005
RBP: 00007f8e72c35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8e72e26038 R14: 00007f8e72e25fa0 R15: 00007ffc794b4df8
 </TASK>

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/25 06:28 upstream 66498c75b4f8 23caa175 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in blk_mq_alloc_tag_set
2026/08/21 07:59 upstream 7f063b2f17ea 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in blk_mq_alloc_tag_set
2026/08/18 12:34 upstream ff68e5f557f6 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root WARNING in blk_mq_alloc_tag_set
2026/07/24 12:53 upstream d326f83e819c 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in blk_mq_alloc_tag_set
2026/08/19 17:44 linux-next 6a746cd265ae 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in blk_mq_alloc_tag_set
2026/08/19 17:40 linux-next 6a746cd265ae 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in blk_mq_alloc_tag_set
2026/08/18 05:21 linux-next e6664f2b33db 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in blk_mq_alloc_tag_set
2026/08/13 07:05 linux-next 28d012efb432 67796a05 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in blk_mq_alloc_tag_set
* Struck through repros no longer work on HEAD.