KASAN: slab-use-after-free Read in atkbd_event_work

Status: upstream: reported on 2026/08/29 01:05
Subsystems: kernel
Labels: prio:high actionable
[Documentation on labels]
Reported-by: syzbot+f8a0f50ead274d8516d3@syzkaller.appspotmail.com
First crash: 4d20h, last: 2d08h
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
fe58353b moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Read in atkbd_event_work 2026/08/29 00:29 2026/08/29 00:29 2026/08/29 01:04 bcbc8ceb
072de4ee repro-c Reproduced: ✅ ❓ KASAN: slab-use-after-free Read in atkbd_event_work 2026/08/27 19:16 2026/08/27 19:17 2026/08/27 20:09 bd6de8ec
c41210c1 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in atkbd_event_work 2026/08/26 00:42 2026/08/26 00:42 2026/08/26 01:25 ee98d2fd
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [kernel?] KASAN: slab-use-after-free Read in atkbd_event_work 1 (2) 2026/08/29 04:54
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/08/28 10:08 15m nogikh@google.com git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 818bebeb63dd6bf5f4e07e145f6cdbace520a34c report job log log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in atkbd_event_work+0x592/0x650 drivers/input/keyboard/atkbd.c:-1
Read of size 4 at addr ffff888025c96164 by task kworker/1:2/3686

CPU: 1 UID: 0 PID: 3686 Comm: kworker/1:2 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Workqueue: events atkbd_event_work
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 atkbd_event_work+0x592/0x650 drivers/input/keyboard/atkbd.c:-1
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
 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>

Allocated by task 5621:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x321/0x600 mm/slub.c:5563
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 input_allocate_device+0x4e/0x2a0 drivers/input/input.c:1960
 atkbd_connect+0xb1/0x9c0 drivers/input/keyboard/atkbd.c:1258
 serio_connect_driver drivers/input/serio/serio.c:44 [inline]
 serio_driver_probe+0x82/0xa0 drivers/input/serio/serio.c:748
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x254/0xae0 drivers/base/dd.c:706
 __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
 __device_attach_driver+0x270/0x410 drivers/base/dd.c:1026
 bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c4/0x450 drivers/base/dd.c:1098
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x12a/0x220 drivers/base/bus.c:620
 device_add+0x7d7/0xb80 drivers/base/core.c:3776
 serio_add_port drivers/input/serio/serio.c:512 [inline]
 serio_handle_event+0x9f2/0xd20 drivers/input/serio/serio.c:197
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
 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

Freed by task 8139:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2748 [inline]
 slab_free mm/slub.c:6499 [inline]
 kfree+0x1c5/0x650 mm/slub.c:6792
 input_dev_release+0xab/0xc0 drivers/input/input.c:1644
 device_release+0xc4/0x1f0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x222/0x550 lib/kobject.c:737
 atkbd_disconnect+0xb5/0x110 drivers/input/keyboard/atkbd.c:966
 serio_disconnect_driver drivers/input/serio/serio.c:62 [inline]
 serio_driver_remove+0x85/0xa0 drivers/input/serio/serio.c:755
 device_remove drivers/base/dd.c:616 [inline]
 __device_release_driver drivers/base/dd.c:1349 [inline]
 device_release_driver_internal+0x48b/0x880 drivers/base/dd.c:1372
 serio_disconnect_port drivers/input/serio/serio.c:646 [inline]
 serio_unregister_port+0x128/0x150 drivers/input/serio/serio.c:679
 userio_char_release+0x80/0xc0 drivers/input/serio/userio.c:105
 __fput+0x418/0xa50 fs/file_table.c:512
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x204/0x770 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
 do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888025c96000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 356 bytes inside of
 freed 4096-byte region [ffff888025c96000, ffff888025c97000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x25c90
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b042140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b042140 dead000000000100 dead000000000122
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4978, tgid 4978 (udevd), ts 44140195112
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x2209/0x2280 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x217/0x5a0 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3347 [inline]
 allocate_slab+0x7d/0x620 mm/slub.c:3462
 new_slab mm/slub.c:3513 [inline]
 refill_objects+0x2d5/0x350 mm/slub.c:7410
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x2c8/0x6c0 mm/slub.c:4774
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 __do_kmalloc_node mm/slub.c:5413 [inline]
 __kmalloc_noprof+0x47b/0x720 mm/slub.c:5439
 _kmalloc_noprof include/linux/slab.h:995 [inline]
 tomoyo_realpath_from_path+0xef/0x640 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x229/0x470 security/tomoyo/file.c:776
 security_file_open+0xa9/0x240 security/security.c:2739
 do_dentry_open+0x4a0/0x1380 fs/open.c:973
 vfs_open+0x3b/0x340 fs/open.c:1101
 do_open fs/namei.c:4837 [inline]
 path_openat+0x1443/0x1d60 fs/namei.c:5000
 do_file_open+0x23e/0x4a0 fs/namei.c:5029
 do_sys_openat2+0x115/0x200 fs/open.c:1417
 do_sys_open fs/open.c:1423 [inline]
 __do_sys_openat fs/open.c:1439 [inline]
 __se_sys_openat fs/open.c:1434 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1434
page last free pid 4981 tgid 4981 ts 44132500299 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0xc93/0xd90 mm/page_alloc.c:2962
 __slab_free+0x274/0x2c0 mm/slub.c:5815
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4683 [inline]
 slab_alloc_node mm/slub.c:4996 [inline]
 __kmalloc_cache_noprof+0x29f/0x600 mm/slub.c:5559
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 kernfs_iop_get_link+0x66/0x6c0 fs/kernfs/symlink.c:137
 vfs_readlink+0x24a/0x540 fs/namei.c:6419
 do_readlinkat+0x218/0x510 fs/stat.c:583
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x7f/0x90 fs/stat.c:602
 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

Memory state around the buggy address:
 ffff888025c96000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888025c96080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888025c96100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff888025c96180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888025c96200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/25 13:36 upstream 66498c75b4f8 614e416a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KASAN: slab-use-after-free Read in atkbd_event_work
2026/08/27 05:04 upstream 818bebeb63dd a2b77b9e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in atkbd_event_work
2026/08/24 16:44 upstream 818bebeb63dd b55bd4c3 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in atkbd_event_work
* Struck through repros no longer work on HEAD.