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

Status: upstream: reported on 2026/06/01 19:31
Subsystems: serial
Labels: prio:high actionable
[Documentation on labels]
Reported-by: syzbot+2932e8970a6398db95c3@syzkaller.appspotmail.com
First crash: 152d, last: 14d
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
fb20c2c4 repro-c Reproduced: ✅ ❓ KASAN: slab-use-after-free Read in stop_tty 2026/09/27 11:12 2026/09/27 11:12 2026/09/27 12:15 a3c7249d
780c1674 moderation Actionable: ✅ ❓ KASAN: slab-use-after-free Read in stop_tty 2026/06/01 18:24 2026/06/01 18:35 2026/06/01 19:30 386cc6da
3f7916dd assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ✅ ❓ KASAN: slab-use-after-free Read in stop_tty 2026/05/29 20:12 2026/05/29 20:12 2026/05/29 20:53 6b4a8443
▶ ▼ Discussions (4)
Title Replies (including bot) Last reply
[syzbot] Monthly serial report (Sep 2026) 0 (1) 2026/09/04 12:33
[syzbot] Monthly serial report (Aug 2026) 0 (1) 2026/08/04 12:32
[PATCH] tty: vt: hold tty reference for keyboard callbacks 2 (2) 2026/06/03 06:12
[syzbot] [serial?] KASAN: slab-use-after-free Read in stop_tty 0 (1) 2026/06/01 19:31
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/09/27 23:35 1h09m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git efb44d93a620c294c049db37c810c8ab7ee1122d report job log log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:155 [inline]
BUG: KASAN: slab-use-after-free in _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:181
Read of size 1 at addr ffff8880516a2418 by task syz.2.408/7888

CPU: 1 UID: 0 PID: 7888 Comm: syz.2.408 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
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
 __kasan_check_byte+0x2a/0x40 mm/kasan/common.c:585
 kasan_check_byte include/linux/kasan.h:402 [inline]
 lock_acquire+0x7d/0x350 kernel/locking/lockdep.c:5916
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:155 [inline]
 _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:181
 rtlock_slowlock kernel/locking/rtmutex.c:1921 [inline]
 rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
 __rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
 rt_spin_lock+0x157/0x400 kernel/locking/spinlock_rt.c:57
 spin_lock include/linux/spinlock_rt.h:45 [inline]
 class_spinlock_irqsave_constructor include/linux/spinlock.h:643 [inline]
 stop_tty+0x2e/0x110 drivers/tty/tty_io.c:767
 kbd_keycode drivers/tty/vt/keyboard.c:1574 [inline]
 kbd_event+0x2e8d/0x41f0 drivers/tty/vt/keyboard.c:1592
 input_handle_events_default+0xd4/0x1a0 drivers/input/input.c:2614
 input_pass_values+0x288/0x890 drivers/input/input.c:128
 input_event_dispose+0x35f/0x700 drivers/input/input.c:342
 input_inject_event+0x1fa/0x310 drivers/input/input.c:424
 evdev_write+0x328/0x4c0 drivers/input/evdev.c:533
 vfs_write+0x29f/0xbb0 fs/read_write.c:685
 ksys_write+0x156/0x270 fs/read_write.c:739
 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
RIP: 0033:0x7fe3d969e1d9
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:00007fe3d78d5028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fe3d9926090 RCX: 00007fe3d969e1d9
RDX: 0000000000002250 RSI: 0000200000000040 RDI: 0000000000000003
RBP: 00007fe3d9735888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe3d9926128 R14: 00007fe3d9926090 R15: 00007ffefe5fb2c8
 </TASK>

Allocated by task 7886:
 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:409 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:426
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x3d5/0x680 mm/slub.c:5563
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 alloc_tty_struct+0xa6/0x7c0 drivers/tty/tty_io.c:3092
 tty_init_dev+0x59/0x4d0 drivers/tty/tty_io.c:1375
 tty_open_by_driver drivers/tty/tty_io.c:2048 [inline]
 tty_open+0x7e5/0xcd0 drivers/tty/tty_io.c:2095
 chrdev_open+0x4dc/0x600 fs/char_dev.c:411
 do_dentry_open+0x849/0x1420 fs/open.c:996
 vfs_open+0x3b/0x350 fs/open.c:1101
 do_open fs/namei.c:4866 [inline]
 path_openat+0x1448/0x1d60 fs/namei.c:5029
 do_file_open+0x23e/0x4a0 fs/namei.c:5058
 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
 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

Freed by task 10:
 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:264 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:296
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2748 [inline]
 slab_free mm/slub.c:6509 [inline]
 kfree+0x1c5/0x6d0 mm/slub.c:6802
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x470 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

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:57
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
 insert_work+0x3d/0x330 kernel/workqueue.c:2272
 __queue_work+0xd4e/0x1130 kernel/workqueue.c:2448
 queue_work_on+0x106/0x1d0 kernel/workqueue.c:2501
 tty_release_struct+0xb8/0xd0 drivers/tty/tty_io.c:1667
 tty_release+0xc6b/0x1680 drivers/tty/tty_io.c:1827
 __fput+0x41f/0xa80 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:343 [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 ffff8880516a2000
 which belongs to the cache kmalloc-cg-4k of size 4096
The buggy address is located 1048 bytes inside of
 freed 4096-byte region [ffff8880516a2000, ffff8880516a3000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x516a0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff8880516a1011
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813ff08500 dead000000000100 dead000000000122
raw: 0000000000000000 0000000300040004 00000000f5000000 ffff8880516a1011
head: 0080000000000040 ffff88813ff08500 dead000000000100 dead000000000122
head: 0000000000000000 0000000300040004 00000000f5000000 ffff8880516a1011
head: 0080000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6086, tgid 6086 (syz-executor), ts 243287552474
 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+0x2591/0x2600 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x230/0x5c0 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+0x2d8/0x350 mm/slub.c:7418
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x339/0x690 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_node_track_caller_noprof+0x61e/0x7b0 mm/slub.c:5545
 kmemdup_noprof+0x2b/0x70 mm/util.c:138
 kmemdup_noprof include/linux/fortify-string.h:715 [inline]
 __addrconf_sysctl_register+0xa7/0x4b0 net/ipv6/addrconf.c:7334
 addrconf_sysctl_register+0x168/0x1c0 net/ipv6/addrconf.c:7400
 ipv6_add_dev+0xd64/0x1400 net/ipv6/addrconf.c:460
 addrconf_notify+0x771/0x1050 net/ipv6/addrconf.c:3686
 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2313 [inline]
 call_netdevice_notifiers net/core/dev.c:2327 [inline]
 register_netdevice+0x18c0/0x1ed0 net/core/dev.c:11587
 veth_newlink+0x6a2/0xdd0 drivers/net/veth.c:1902
 rtnl_newlink_create+0x305/0x7b0 net/core/rtnetlink.c:3974
page last free pid 6393 tgid 6393 ts 238908516627 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0xf8e/0x1070 mm/page_alloc.c:2962
 __slab_free+0x250/0x2a0 mm/slub.c:5823
 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:361
 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]
 __do_kmalloc_node mm/slub.c:5413 [inline]
 __kmalloc_noprof+0x3b9/0x790 mm/slub.c:5439
 _kmalloc_noprof include/linux/slab.h:995 [inline]
 load_elf_phdrs fs/binfmt_elf.c:537 [inline]
 load_elf_binary+0x2ca/0x28f0 fs/binfmt_elf.c:866
 search_binary_handler fs/exec.c:1779 [inline]
 exec_binprm fs/exec.c:1811 [inline]
 bprm_execve+0x930/0x1590 fs/exec.c:1867
 kernel_execve+0x8c3/0x9c0 fs/exec.c:2011
 call_usermodehelper_exec_async+0x212/0x360 kernel/umh.c:107
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff8880516a2300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880516a2380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880516a2400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8880516a2480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880516a2500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/13 04:29 upstream 24a19b953e2a 745a967f .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in stop_tty
2026/09/03 08:51 upstream 940de590b839 6a988719 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in stop_tty
2026/08/24 19:05 upstream 0a0d1d55dad5 23caa175 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in stop_tty
2026/07/07 20:20 upstream 0e35b9b6ec0f 88a4b44c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in stop_tty
2026/05/28 17:58 upstream eb3f4b7426cf 9a5a7e5e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in stop_tty
2026/07/30 02:59 linux-next cc2b5f627e8c cb1587ea .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in stop_tty
* Struck through repros no longer work on HEAD.