KCSAN: data-race in mas_wmb_replace / mtree_load

Status: moderation: reported on 2026/07/24 16:35
Subsystems: kernel
Labels: race:benign prio:low
[Documentation on labels]
Reported-by: syzbot+0d74f91215c2017478aa@syzkaller.appspotmail.com
First crash: 35d, last: 3d21h
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
6a11cb04 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ KCSAN: data-race in mas_wmb_replace / mtree_load 2026/07/26 00:00 2026/07/26 00:00 2026/07/26 00:37 492bab15
c878abb1 assessment-kcsan Benign: ✅ KCSAN: data-race in mas_wmb_replace / mtree_load 2026/07/24 16:34 2026/07/24 16:34 2026/07/24 17:16 1bdb5c57

Sample crash report:
virtio_scsi virtio0: 1/0/0 default/read/poll queues
==================================================================
BUG: KCSAN: data-race in mas_wmb_replace / mtree_load

write to 0xffff888105c2cb00 of 8 bytes by task 1618 on cpu 0:
 mte_set_node_dead lib/maple_tree.c:299 [inline]
 mas_topiary_node lib/maple_tree.c:1792 [inline]
 mas_topiary_replace lib/maple_tree.c:1898 [inline]
 mas_wmb_replace+0x1512/0x1770 lib/maple_tree.c:2083
 mas_wr_store_entry+0x54a7/0x5a90 lib/maple_tree.c:-1
 mas_store_gfp+0x5cd/0x6c0 lib/maple_tree.c:4905
 irq_insert_desc kernel/irq/irqdesc.c:195 [inline]
 alloc_descs kernel/irq/irqdesc.c:531 [inline]
 __irq_alloc_descs+0x361/0x4d0 kernel/irq/irqdesc.c:922
 irq_domain_alloc_descs kernel/irq/irqdomain.c:-1 [inline]
 irq_domain_alloc_irqs_locked+0x7f/0x7d0 kernel/irq/irqdomain.c:1639
 __irq_domain_alloc_irqs+0x80/0xd0 kernel/irq/irqdomain.c:1713
 __msi_domain_alloc_irqs+0x435/0xa00 kernel/irq/msi.c:1336
 __msi_domain_alloc_locked kernel/irq/msi.c:1393 [inline]
 msi_domain_alloc_locked+0x357/0x3e0 kernel/irq/msi.c:1398
 msi_domain_alloc_irqs_all_locked+0xd2/0x110 kernel/irq/msi.c:1474
 pci_msi_setup_msi_irqs+0x7a/0x90 drivers/pci/msi/irqdomain.c:17
 __msix_setup_interrupts drivers/pci/msi/msi.c:687 [inline]
 msix_setup_interrupts drivers/pci/msi/msi.c:708 [inline]
 msix_capability_init+0x566/0x960 drivers/pci/msi/msi.c:748
 __pci_enable_msix_range+0x41d/0x4b0 drivers/pci/msi/msi.c:856
 pci_alloc_irq_vectors_affinity+0xac/0x1e0 drivers/pci/msi/api.c:268
 vp_request_msix_vectors drivers/virtio/virtio_pci_common.c:157 [inline]
 vp_find_vqs_msix+0x3f0/0x8b0 drivers/virtio/virtio_pci_common.c:414
 vp_find_vqs+0x4a/0x4a0 drivers/virtio/virtio_pci_common.c:524
 virtio_find_vqs include/linux/virtio_config.h:298 [inline]
 virtio_find_single_vq include/linux/virtio_config.h:309 [inline]
 probe_common+0x1e8/0x3c0 drivers/char/hw_random/virtio-rng.c:177
 virtrng_restore+0x1a/0xc0 drivers/char/hw_random/virtio-rng.c:243
 virtio_device_restore_priv+0x23c/0x410 drivers/virtio/virtio.c:646
 virtio_device_restore+0x1a/0x30 drivers/virtio/virtio.c:693
 virtio_pci_restore drivers/virtio/virtio_pci_common.c:621 [inline]
 virtio_pci_resume+0xfa/0x140 drivers/virtio/virtio_pci_common.c:648
 pci_pm_resume+0x160/0x340 drivers/pci/pci-driver.c:1065
 dpm_run_callback+0x53/0x2f0 drivers/base/power/main.c:513
 device_resume+0x76f/0x7a0 drivers/base/power/main.c:1192
 async_resume+0x2c/0x40 drivers/base/power/main.c:1215
 async_run_entry_fn+0x52/0x180 kernel/async.c:129
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0x56a/0xa50 kernel/workqueue.c:3470
 worker_thread+0x569/0x750 kernel/workqueue.c:3551
 kthread+0x223/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888105c2cb00 of 8 bytes by task 13210 on cpu 1:
 ma_dead_node lib/maple_tree.c:544 [inline]
 mtree_lookup_walk lib/maple_tree.c:2988 [inline]
 mtree_load+0x3fd/0x600 lib/maple_tree.c:5668
 irq_to_desc kernel/irq/irqdesc.c:414 [inline]
 __irq_get_desc_lock+0x29/0x130 kernel/irq/irqdesc.c:946
 class_irqdesc_lock_constructor kernel/irq/internals.h:205 [inline]
 irq_set_msi_desc_off+0x59/0x160 kernel/irq/chip.c:100
 __msi_domain_alloc_irqs+0x486/0xa00 kernel/irq/msi.c:1343
 __msi_domain_alloc_locked kernel/irq/msi.c:1393 [inline]
 msi_domain_alloc_locked+0x357/0x3e0 kernel/irq/msi.c:1398
 msi_domain_alloc_irqs_all_locked+0xd2/0x110 kernel/irq/msi.c:1474
 pci_msi_setup_msi_irqs+0x7a/0x90 drivers/pci/msi/irqdomain.c:17
 __msix_setup_interrupts drivers/pci/msi/msi.c:687 [inline]
 msix_setup_interrupts drivers/pci/msi/msi.c:708 [inline]
 msix_capability_init+0x566/0x960 drivers/pci/msi/msi.c:748
 __pci_enable_msix_range+0x41d/0x4b0 drivers/pci/msi/msi.c:856
 pci_alloc_irq_vectors_affinity+0xac/0x1e0 drivers/pci/msi/api.c:268
 vp_request_msix_vectors drivers/virtio/virtio_pci_common.c:157 [inline]
 vp_find_vqs_msix+0x3f0/0x8b0 drivers/virtio/virtio_pci_common.c:414
 vp_find_vqs+0x4a/0x4a0 drivers/virtio/virtio_pci_common.c:524
 virtio_find_vqs include/linux/virtio_config.h:298 [inline]
 virtscsi_init+0x50b/0x8b0 drivers/scsi/virtio_scsi.c:886
 virtscsi_restore+0x3a/0xf0 drivers/scsi/virtio_scsi.c:1025
 virtio_device_restore_priv+0x23c/0x410 drivers/virtio/virtio.c:646
 virtio_device_restore+0x1a/0x30 drivers/virtio/virtio.c:693
 virtio_pci_restore drivers/virtio/virtio_pci_common.c:621 [inline]
 virtio_pci_resume+0xfa/0x140 drivers/virtio/virtio_pci_common.c:648
 pci_pm_resume+0x160/0x340 drivers/pci/pci-driver.c:1065
 dpm_run_callback+0x53/0x2f0 drivers/base/power/main.c:513
 device_resume+0x76f/0x7a0 drivers/base/power/main.c:1192
 async_resume+0x2c/0x40 drivers/base/power/main.c:1215
 async_run_entry_fn+0x52/0x180 kernel/async.c:129
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0x56a/0xa50 kernel/workqueue.c:3470
 worker_thread+0x569/0x750 kernel/workqueue.c:3551
 kthread+0x223/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0xffff88810963160e -> 0xffff888105c2cb00

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13210 Comm: kworker/u8:52 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: async async_run_entry_fn
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/25 08:59 upstream 66498c75b4f8 614e416a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wmb_replace / mtree_load
2026/07/24 16:34 upstream 48a5a7ab8d6a dd737a83 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mas_wmb_replace / mtree_load
* Struck through repros no longer work on HEAD.