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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: 55d, last: 14d
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
780c1674-13b3-4511-8566-1b254f6eb645 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 386cc6dacdf7e3ebce9507beed6755d7e999554d 

			
				
	

	
	

		3f7916dd-68a8-4f34-a7bf-018f0f009276
		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
		6b4a844333e83556da95d61d7f207e7ef5cd4bc6
		
			

			
				
	

	
	



			

		

	

	
	

		

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			[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
		

	
	




			
			
		

	

	

	
	
Sample crash report:

	
==================================================================
BUG: KASAN: slab-use-after-free in __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
BUG: KASAN: slab-use-after-free in _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:166
Read of size 1 at addr ffff888055836418 by task syz.4.1714/13395

CPU: 1 UID: 0 PID: 13395 Comm: syz.4.1714 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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:574
 kasan_check_byte include/linux/kasan.h:402 [inline]
 lock_acquire+0x84/0x350 kernel/locking/lockdep.c:5842
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
 _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:166
 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:620 [inline]
 stop_tty+0x2e/0x110 drivers/tty/tty_io.c:765
 kbd_keycode drivers/tty/vt/keyboard.c:1565 [inline]
 kbd_event+0x2e95/0x41f0 drivers/tty/vt/keyboard.c:1583
 input_handle_events_default+0xd4/0x1a0 drivers/input/input.c:2561
 input_pass_values+0x288/0x890 drivers/input/input.c:128
 input_event_dispose+0x330/0x6b0 drivers/input/input.c:342
 input_inject_event+0x1fa/0x310 drivers/input/input.c:424
 evdev_write+0x328/0x4c0 drivers/input/evdev.c:528
 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:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f32327cde59
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:00007f3230a26028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f3232a55fa0 RCX: 00007f32327cde59
RDX: 0000000000002250 RSI: 0000200000000040 RDI: 0000000000000008
RBP: 00007f3232863e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3232a56038 R14: 00007f3232a55fa0 R15: 00007ffe89e9fa68
 </TASK>

Allocated by task 13395:
 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+0x3d2/0x6b0 mm/slub.c:5515
 _kmalloc_noprof include/linux/slab.h:969 [inline]
 _kzalloc_noprof include/linux/slab.h:1290 [inline]
 alloc_tty_struct+0xa6/0x7a0 drivers/tty/tty_io.c:3102
 tty_init_dev+0x59/0x4d0 drivers/tty/tty_io.c:1400
 tty_open_by_driver drivers/tty/tty_io.c:2073 [inline]
 tty_open+0x7e5/0xcd0 drivers/tty/tty_io.c:2120
 chrdev_open+0x4dc/0x600 fs/char_dev.c:411
 do_dentry_open+0x849/0x1420 fs/open.c:947
 vfs_open+0x3b/0x350 fs/open.c:1052
 do_open fs/namei.c:4700 [inline]
 path_openat+0x2e60/0x3850 fs/namei.c:4863
 do_file_open+0x23e/0x4a0 fs/namei.c:4892
 do_sys_openat2+0x115/0x200 fs/open.c:1368
 do_sys_open fs/open.c:1374 [inline]
 __do_sys_openat fs/open.c:1390 [inline]
 __se_sys_openat fs/open.c:1385 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1385
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5588:
 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:2705 [inline]
 slab_free mm/slub.c:6405 [inline]
 kfree+0x1c5/0x6c0 mm/slub.c:6720
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 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:2226
 __queue_work+0xd1d/0x10f0 kernel/workqueue.c:2401
 queue_work_on+0x106/0x1d0 kernel/workqueue.c:2452
 tty_release_struct+0xb8/0xd0 drivers/tty/tty_io.c:1692
 tty_release+0xc6b/0x1680 drivers/tty/tty_io.c:1852
 __fput+0x42a/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+0x1fa/0x730 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:318 [inline]
 do_syscall_64+0x353/0x580 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888055836000
 which belongs to the cache kmalloc-cg-2k of size 2048
The buggy address is located 1048 bytes inside of
 freed 2048-byte region [ffff888055836000, ffff888055836800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888055831000 pfn:0x55830
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888055830811
flags: 0x80000000000240(workingset|head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000240 ffff88813ff0d3c0 ffffea0000e1e010 ffffea0000cc4e10
raw: ffff888055831000 0000100000080007 00000000f5000000 ffff888055830811
head: 0080000000000240 ffff88813ff0d3c0 ffffea0000e1e010 ffffea0000cc4e10
head: ffff888055831000 0000100000080007 00000000f5000000 ffff888055830811
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 8505, tgid 8505 (syz-executor), ts 534917153490, free_ts 534882040608
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0x262a/0x26a0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3294 [inline]
 allocate_slab+0x79/0x5e0 mm/slub.c:3408
 new_slab mm/slub.c:3454 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7338
 refill_sheaf mm/slub.c:2832 [inline]
 __pcs_replace_empty_main+0x330/0x690 mm/slub.c:4703
 alloc_from_pcs mm/slub.c:4801 [inline]
 slab_alloc_node mm/slub.c:4933 [inline]
 __do_kmalloc_node mm/slub.c:5361 [inline]
 __kmalloc_node_track_caller_noprof+0x62d/0x7c0 mm/slub.c:5497
 kmemdup_noprof+0x2b/0x70 mm/util.c:138
 kmemdup_noprof include/linux/fortify-string.h:715 [inline]
 neigh_sysctl_register+0xae/0xa90 net/core/neighbour.c:3854
 addrconf_sysctl_register+0xb3/0x1c0 net/ipv6/addrconf.c:7410
 ipv6_add_dev+0xd64/0x1400 net/ipv6/addrconf.c:460
 addrconf_notify+0x771/0x1050 net/ipv6/addrconf.c:3685
 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2288 [inline]
 call_netdevice_notifiers net/core/dev.c:2302 [inline]
 register_netdevice+0x18c0/0x1ed0 net/core/dev.c:11478
 rtnl_newlink_create+0x31f/0xb00 net/core/rtnetlink.c:3915
 __rtnl_newlink net/core/rtnetlink.c:4044 [inline]
 rtnl_newlink+0x167f/0x1bd0 net/core/rtnetlink.c:4159
page last free pid 3324 tgid 3324 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0x10e7/0x11c0 mm/page_alloc.c:2950
 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
 netdev_run_todo+0xf56/0x10d0 net/core/dev.c:11749
 default_device_exit_batch+0x966/0x9e0 net/core/dev.c:13094
 ops_exit_list net/core/net_namespace.c:205 [inline]
 ops_undo_list+0x4b4/0x8d0 net/core/net_namespace.c:252
 cleanup_net+0x575/0x810 net/core/net_namespace.c:702
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 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

Memory state around the buggy address:
 ffff888055836300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888055836380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888055836400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888055836480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888055836500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================



	

	



	Crashes (2):
		
		

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			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
		

		
		


* Struck through repros no longer work on HEAD.