WARNING in mmc_free_host

Status: upstream: reported on 2026/08/19 18:13
Subsystems: mmc
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+82a0a7de6d84867d030e@syzkaller.appspotmail.com
First crash: 27d, last: 7h42m
✨ AI Jobs (4)
ID Workflow Result Correct Bug Created Started Finished Revision
2edec3cb repro-c Reproduced: ✅ WARNING in mmc_free_host 2026/09/04 19:36 2026/09/04 19:36 2026/09/04 21:17 7ce8fcf4
f5ecb5e5 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in mmc_free_host 2026/08/22 00:47 2026/08/22 00:47 2026/08/22 01:40 1e72964b
8664227c assessment-security 💥 WARNING in mmc_free_host 2026/08/19 01:37 2026/08/19 01:37 2026/08/19 01:37 1e72964b
ef5561ba assessment-security 💥 WARNING in mmc_free_host 2026/08/17 02:15 2026/08/17 02:15 2026/08/17 02:15 746171ee
Discussions (2)
Title Replies (including bot) Last reply
[syzbot] Monthly mmc report (Sep 2026) 0 (1) 2026/09/02 20:33
[syzbot] [mmc?] WARNING in mmc_free_host 0 (1) 2026/08/19 18:13
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 WARNING in mmc_free_host -1 1 21d 21d 0/2 upstream: reported on 2026/08/20 22:09
Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/09/04 21:17 14m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git bc35965f6940a9bf834d54187b6088b8eb09206d report job log log

Sample crash report:
------------[ cut here ]------------
do not call blocking ops when !TASK_RUNNING; state=402 set at [<ffffffff8a3f944a>] ip_vs_estimation_kthread+0x283a/0x3950 net/netfilter/ipvs/ip_vs_est.c:204
WARNING: kernel/sched/core.c:9183 at __might_sleep+0x92/0xf0 kernel/sched/core.c:9179, CPU#1: ipvs-e:15:0/13057
Modules linked in:
CPU: 1 UID: 0 PID: 13057 Comm: ipvs-e:15:0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
RIP: 0010:__might_sleep+0xac/0xf0 kernel/sched/core.c:9179
Code: 00 00 48 89 3c 24 41 89 f5 4c 8d 35 4e 9c e6 0e 43 80 3c 3c 00 74 08 48 89 df e8 ff 44 a1 00 48 8b 0b 4c 89 f7 89 ee 48 89 ca <67> 48 0f b9 3a 44 89 ee 48 8b 3c 24 eb b5 44 89 f1 80 e1 07 80 c1
RSP: 0018:ffffc90000a18c08 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88801dbe7668 RCX: ffffffff8a3f944a
RDX: ffffffff8a3f944a RSI: 0000000000000402 RDI: ffffffff907d1ca0
RBP: 0000000000000402 R08: 0000000000000100 R09: 1ffffffff20f43cf
R10: dffffc0000000000 R11: fffffbfff20f43d0 R12: 1ffff11003b7cecd
R13: 00000000000011d1 R14: ffffffff907d1ca0 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888124dd6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f792c3556c8 CR3: 000000001dfe5000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 __cancel_work_sync+0x6d/0x110 kernel/workqueue.c:4561
 mmc_free_host+0x19/0x30 drivers/mmc/core/host.c:700
 call_timer_fn+0x18d/0x5f0 kernel/time/timer.c:1748
 expire_timers kernel/time/timer.c:1799 [inline]
 __run_timers kernel/time/timer.c:2374 [inline]
 __run_timer_base+0x652/0x8b0 kernel/time/timer.c:2386
 run_timer_base kernel/time/timer.c:2395 [inline]
 run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2405
 handle_softirqs+0x226/0x860 kernel/softirq.c:645
 __do_softirq kernel/softirq.c:679 [inline]
 invoke_softirq kernel/softirq.c:519 [inline]
 __irq_exit_rcu+0xcb/0x220 kernel/softirq.c:758
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:775
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:211 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x47/0x80 kernel/locking/spinlock.c:221
Code: f7 e8 0d 6f bc f5 f7 c3 00 02 00 00 74 05 e8 f0 b1 e8 f5 9c 58 a9 00 02 00 00 75 29 f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 14 7e ad f5 65 48 8b 05 0c 41 ad 07 48 85 c0 74 18 5b 41 5e e9
RSP: 0018:ffffc9000469f9c8 EFLAGS: 00000206
RAX: 0000000000000006 RBX: 0000000000000287 RCX: 8000000000000001
RDX: 0000000000000000 RSI: ffffffff8e474d50 RDI: 0000000000000001
RBP: dffffc0000000000 R08: ffffffff907a1e7f R09: 1ffffffff20f43cf
R10: dffffc0000000000 R11: fffffbfff20f43d0 R12: ffff8880b8726100
R13: 0000000000000000 R14: ffff8880b8726100 R15: 0000000000000287
 __mod_timer+0xb53/0xed0 kernel/time/timer.c:1139
 schedule_timeout+0x14d/0x2c0 kernel/time/sleep_timeout.c:98
 ip_vs_estimation_kthread+0x29ef/0x3950 net/netfilter/ipvs/ip_vs_est.c:216
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
----------------
Code disassembly (best guess):
   0:	00 00                	add    %al,(%rax)
   2:	48 89 3c 24          	mov    %rdi,(%rsp)
   6:	41 89 f5             	mov    %esi,%r13d
   9:	4c 8d 35 4e 9c e6 0e 	lea    0xee69c4e(%rip),%r14        # 0xee69c5e
  10:	43 80 3c 3c 00       	cmpb   $0x0,(%r12,%r15,1)
  15:	74 08                	je     0x1f
  17:	48 89 df             	mov    %rbx,%rdi
  1a:	e8 ff 44 a1 00       	call   0xa1451e
  1f:	48 8b 0b             	mov    (%rbx),%rcx
  22:	4c 89 f7             	mov    %r14,%rdi
  25:	89 ee                	mov    %ebp,%esi
  27:	48 89 ca             	mov    %rcx,%rdx
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	44 89 ee             	mov    %r13d,%esi
  32:	48 8b 3c 24          	mov    (%rsp),%rdi
  36:	eb b5                	jmp    0xffffffed
  38:	44 89 f1             	mov    %r14d,%ecx
  3b:	80 e1 07             	and    $0x7,%cl
  3e:	80                   	.byte 0x80
  3f:	c1                   	.byte 0xc1

Crashes (19):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/08 21:43 upstream 28924df2a08f 243b72f1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in mmc_free_host
2026/09/06 18:31 upstream 1fc5a74b108f 4f7b22a0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in mmc_free_host
2026/09/05 00:18 upstream bc35965f6940 3f042c7b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in mmc_free_host
2026/09/04 04:48 upstream 841e384b841a 801f0966 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in mmc_free_host
2026/09/03 16:06 upstream 940de590b839 6a988719 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in mmc_free_host
2026/09/02 06:13 upstream 89a312991dc6 587f6b29 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in mmc_free_host
2026/08/31 14:17 upstream cee9395acd80 2f52988a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in mmc_free_host
2026/08/29 02:56 upstream 1b78070aaef6 bcbc8ceb .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in mmc_free_host
2026/08/26 05:31 upstream 45c13f3f9e3b 6a91adb4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in mmc_free_host
2026/08/25 10:01 upstream 66498c75b4f8 614e416a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in mmc_free_host
2026/08/22 09:24 upstream 26260251022f 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in mmc_free_host
2026/08/21 11:59 upstream 818bebeb63dd 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in mmc_free_host
2026/09/11 13:02 upstream 50d05c7c76c9 b6a5eeb7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in mmc_free_host
2026/09/02 04:04 upstream 786262be6048 587f6b29 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in mmc_free_host
2026/08/28 06:33 upstream 1b78070aaef6 e2fa417d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in mmc_free_host
2026/08/25 07:27 upstream 66498c75b4f8 23caa175 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in mmc_free_host
2026/08/17 12:41 upstream 8d3ae59288f1 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in mmc_free_host
2026/08/15 18:09 upstream 15ef2f78c49d 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 WARNING in mmc_free_host
2026/09/03 04:22 linux-next 32b6ef9a5d0e 85995287 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in mmc_free_host
* Struck through repros no longer work on HEAD.