WARNING in iommu_setup_default_domain

Status: upstream: reported on 2026/10/16 03:41
Subsystems: iommu
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+2a4570d89a1e13003dbf@syzkaller.appspotmail.com
First crash: 4d02h, last: 4d02h
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
1ff39bdd repro-c 💥 WARNING in iommu_setup_default_domain 2026/10/15 00:00 2026/10/15 00:00 2026/10/15 00:51 8fb0ae89
5417f174 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ✅ ❓ WARNING in iommu_setup_default_domain 2026/10/13 04:39 2026/10/13 04:39 2026/10/13 05:36 745a967f
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Title Replies (including bot) Last reply
[syzbot] [iommu?] WARNING in iommu_setup_default_domain 0 (1) 2026/10/16 03:41

Sample crash report:
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
------------[ cut here ]------------
ret
WARNING: drivers/iommu/iommu.c:3205 at iommu_setup_default_domain+0xbb6/0xf30 drivers/iommu/iommu.c:3205, CPU#2: syz.2.802/11603
Modules linked in:
CPU: 2 UID: 0 PID: 11603 Comm: syz.2.802 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:iommu_setup_default_domain+0xbb6/0xf30 drivers/iommu/iommu.c:3205
Code: 24 10 48 89 de ba 01 00 00 00 e8 25 5e ff ff 31 ff 41 89 c4 89 c6 e8 79 97 42 fc 45 85 e4 0f 84 37 fc ff ff e8 fb 9c 42 fc 90 <0f> 0b 90 e9 4b fd ff ff e8 ed 9c 42 fc 8b 35 c7 c9 7c 0c 48 8b 7c
RSP: 0018:ffffc90002d87610 EFLAGS: 00010287

RAX: 000000000003c9f5 RBX: ffff88801d082c00 RCX: ffffc9000c001000
RDX: 0000000000080000 RSI: ffffffff85c90575 RDI: ffff888024200000
RBP: dffffc0000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 00000000fffffff4 R11: 0000000000000001 R12: 00000000fffffff4
R13: 0000000000000000 R14: ffff888026609150 R15: ffff888026609048
FS:  0000000000000000(0000) GS:ffff88809594a000(0063) knlGS:00000000f5456b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f7fa8000 CR3: 000000004dc43000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 __iommu_probe_device+0x1174/0x1550 drivers/iommu/iommu.c:678
 iommu_probe_device+0x28/0x130 drivers/iommu/iommu.c:715
 iommu_bus_notifier drivers/iommu/iommu.c:1823 [inline]
 iommu_bus_notifier+0x5b/0x110 drivers/iommu/iommu.c:1815
 notifier_call_chain+0x99/0x3f0 kernel/notifier.c:85
 blocking_notifier_call_chain kernel/notifier.c:380 [inline]
 blocking_notifier_call_chain+0x69/0xa0 kernel/notifier.c:368
 bus_notify+0x56/0x80 drivers/base/bus.c:1086
 device_add+0x1169/0x1970 drivers/base/core.c:3741
 pci_device_add+0xdb6/0x1820 drivers/pci/probe.c:2769
 pci_scan_single_device drivers/pci/probe.c:2794 [inline]
 pci_scan_single_device+0x1d0/0x240 drivers/pci/probe.c:2780
 pci_scan_slot+0x1c9/0x7c0 drivers/pci/probe.c:2877
 pci_scan_child_bus_extend+0x6b/0x7b0 drivers/pci/probe.c:3096
 pci_scan_child_bus drivers/pci/probe.c:3209 [inline]
 pci_rescan_bus+0x18/0x40 drivers/pci/probe.c:3500
 rescan_store+0xfb/0x130 drivers/pci/pci-sysfs.c:474
 bus_attr_store+0x74/0xb0 drivers/base/bus.c:172
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6af/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline]
 __do_fast_syscall_32+0x13a/0x8b0 arch/x86/entry/syscall_32.c:291
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:316
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7fa7fec
Code: Unable to access opcode bytes at 0xf7fa7fc2.
RSP: 002b:00000000f545650c EFLAGS: 00000292 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000080000140
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/12 03:37 upstream b88c841d1164 4f92358f .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in iommu_setup_default_domain
* Struck through repros no longer work on HEAD.