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KASAN: slab-use-after-free Read in skb_dequeue (2)

Status: upstream: reported on 2026/05/19 10:47
Subsystems: bluetooth
Labels: actionable prio:high
[Documentation on labels]
Reported-by: syzbot+d06554f43a8fb48030b0@syzkaller.appspotmail.com
First crash: 58d, last: 1d12h
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
8c50630f-b600-47d8-a938-0417a6099eff assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in skb_dequeue (2) 2026/06/01 14:15 2026/06/01 14:15 2026/06/01 15:05 386cc6dacdf7e3ebce9507beed6755d7e999554d 

			
				
	

	
	

		af26a25d-5bd2-4cc5-9396-923008cebceb
		moderation
		
			
				
					Actionable: ✅
				
			
				
			
		
		❓
		KASAN: slab-use-after-free Read in skb_dequeue (2)
		2026/05/19 10:05
		2026/05/19 10:05
		2026/05/19 10:46
		223544dc3097d6233a385835bc8dba2b716cc5f0
		
			

			
				
	

	
	



			

		

	

	
	

		

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			Discussions (2)
		

		

			
			
			



	
	

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		Replies (including bot)
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			[RFC PATCH] Bluetooth: btusb: wait for rx_work before freeing data on disconnect
			1 (1)
			2026/05/19 15:44
		

	
		

			[syzbot] [bluetooth?] KASAN: slab-use-after-free Read in skb_dequeue (2)
			1 (2)
			2026/05/19 15:35
		

	
	




			
			
		

	

	
	

		

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			Similar bugs (6)
		

		

			




	
	

		
			Kernel
		
		Title
		
			Rank
			
🛈

		
		Repro
		Cause bisect
		Fix bisect
		Count
		Last
		Reported
		
		
		
			Patched
		
		
			Status
		
		
	

	
	
	
		

			upstream
			
				KASAN: slab-use-after-free Read in skb_dequeue
					bluetooth
			
			19
			
			
			
			4
			304d
			
				
					401d
				
			
			
			
			
				0/29
			
			
				
					
						auto-obsoleted due to no activity on 2025/12/10 14:34
					
				
			
			
		

	
		

			android-54
			
				KASAN: use-after-free Read in skb_dequeue
			
			19
			syz
			
			
			1
			1791d
			
				
					1791d
				
			
			
			
			
				0/2
			
			
				
					
						auto-obsoleted due to no activity on 2023/04/23 02:47
					
				
			
			
		

	
		

			android-5-10
			
				KASAN: use-after-free Write in skb_dequeue
			
			22
			
			
			
			1
			5d07h
			
				
					5d07h
				
			
			
			
			
				0/2
			
			
				
					
						premoderation: reported on 2026/07/07 22:41
					
				
			
			
		

	
		

			upstream
			
				general protection fault in skb_dequeue (3)
					wireless
			
			2
			C
			done
			
			6
			1248d
			
				
					1257d
				
			
			
			
			
				22/29
			
			
				
					
						fixed on 2023/06/08 14:41
					
				
			
			
		

	
		

			upstream
			
				general protection fault in skb_dequeue (2)
					bluetooth
			
			19
			C
			inconclusive
			done
			9
			1736d
			
				
					1821d
				
			
			
			
			
				0/29
			
			
				
					
						auto-closed as invalid on 2022/10/03 17:36
					
				
			
			
		

	
		

			linux-4.19
			
				KASAN: use-after-free Read in skb_dequeue (2)
			
			19
			C
			
			done
			2
			1761d
			
				
					1792d
				
			
			
			
			
				1/1
			
			
				
					
						fixed on 2021/10/15 14:38
					
				
			
			
		

	
	





			
			
			
			
		

	

	

	
	
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 ffff88806afe01a8 by task kworker/1:3/5594

CPU: 1 UID: 0 PID: 5594 Comm: kworker/1:3 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: events btusb_rx_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
 __kasan_check_byte+0x2a/0x40 mm/kasan/common.c:574
 kasan_check_byte include/linux/kasan.h:402 [inline]
 lock_acquire+0x7d/0x350 kernel/locking/lockdep.c:5880
 __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]
 skb_dequeue+0x2d/0x150 net/core/skbuff.c:3970
 btusb_rx_work+0x27/0xd0 drivers/bluetooth/btusb.c:2501
 process_one_work+0xaaf/0x1480 kernel/workqueue.c:3379
 process_scheduled_works kernel/workqueue.c:3462 [inline]
 worker_thread+0xb05/0x10d0 kernel/workqueue.c:3543
 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
 </TASK>

Allocated by task 5765:
 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+0x3cd/0x670 mm/slub.c:5486
 _kmalloc_noprof include/linux/slab.h:969 [inline]
 _kzalloc_noprof include/linux/slab.h:1290 [inline]
 btusb_probe+0x3c2/0x31b0 drivers/bluetooth/btusb.c:4136
 usb_probe_interface+0x653/0xc60 drivers/usb/core/driver.c:396
 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+0x25b/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c7/0x450 drivers/base/dd.c:1098
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x12d/0x220 drivers/base/bus.c:620
 device_add+0x7d7/0xb80 drivers/base/core.c:3772
 usb_set_configuration+0x1ad8/0x2180 drivers/usb/core/message.c:2268
 usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
 usb_probe_device+0x1c3/0x3b0 drivers/usb/core/driver.c:291
 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+0x25b/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c7/0x450 drivers/base/dd.c:1098
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153
 bus_probe_device+0x12d/0x220 drivers/base/bus.c:620
 device_add+0x7d7/0xb80 drivers/base/core.c:3772
 usb_new_device+0x98d/0x1610 drivers/usb/core/hub.c:2695
 hub_port_connect drivers/usb/core/hub.c:5567 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 port_event drivers/usb/core/hub.c:5871 [inline]
 hub_event+0x28cf/0x4cf0 drivers/usb/core/hub.c:5953
 process_one_work+0xaaf/0x1480 kernel/workqueue.c:3379
 process_scheduled_works kernel/workqueue.c:3462 [inline]
 worker_thread+0xb05/0x10d0 kernel/workqueue.c:3543
 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

Freed by task 5765:
 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:2706 [inline]
 slab_free mm/slub.c:6380 [inline]
 kfree+0x1c5/0x6c0 mm/slub.c:6695
 usb_unbind_interface+0x295/0x9f0 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:618 [inline]
 __device_release_driver drivers/base/dd.c:1349 [inline]
 device_release_driver_internal+0x4f5/0x880 drivers/base/dd.c:1372
 bus_remove_device+0x449/0x560 drivers/base/bus.c:664
 device_del+0x528/0x8f0 drivers/base/core.c:3961
 usb_disable_device+0x3d4/0x8d0 drivers/usb/core/message.c:1478
 usb_disconnect+0x32d/0x990 drivers/usb/core/hub.c:2345
 hub_port_connect drivers/usb/core/hub.c:5407 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 port_event drivers/usb/core/hub.c:5871 [inline]
 hub_event+0x1bb7/0x4cf0 drivers/usb/core/hub.c:5953
 process_one_work+0xaaf/0x1480 kernel/workqueue.c:3379
 process_scheduled_works kernel/workqueue.c:3462 [inline]
 worker_thread+0xb05/0x10d0 kernel/workqueue.c:3543
 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:2260
 __queue_work+0xd4a/0x1120 kernel/workqueue.c:2436
 queue_delayed_work_on+0x11a/0x1e0 kernel/workqueue.c:2657
 queue_delayed_work include/linux/workqueue.h:714 [inline]
 schedule_delayed_work include/linux/workqueue.h:856 [inline]
 btusb_recv_event drivers/bluetooth/btusb.c:1257 [inline]
 btusb_recv_intr+0x434/0x6c0 drivers/bluetooth/btusb.c:1320
 btusb_intr_complete+0x161/0x4b0 drivers/bluetooth/btusb.c:1505
 __usb_hcd_giveback_urb+0x3b8/0x5f0 drivers/usb/core/hcd.c:1657
 dummy_timer+0xab9/0x4b30 drivers/usb/gadget/udc/dummy_hcd.c:2005
 __run_hrtimer kernel/time/hrtimer.c:2065 [inline]
 __hrtimer_run_queues+0x3eb/0xaf0 kernel/time/hrtimer.c:2122
 hrtimer_run_softirq+0x18f/0x260 kernel/time/hrtimer.c:2139
 handle_softirqs+0x1d9/0x6c0 kernel/softirq.c:626
 __do_softirq kernel/softirq.c:660 [inline]
 run_ktimerd+0x69/0x100 kernel/softirq.c:1155
 smpboot_thread_fn+0x57c/0xa80 kernel/smpboot.c:160
 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

The buggy address belongs to the object at ffff88806afe0000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 424 bytes inside of
 freed 4096-byte region [ffff88806afe0000, ffff88806afe1000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x6afe0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813fe3b140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88813fe3b140 dead000000000100 dead000000000122
head: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4272, tgid 4272 (kworker/u8:19), ts 266159558163
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1870
 prep_new_page mm/page_alloc.c:1878 [inline]
 get_page_from_freelist+0x264c/0x26c0 mm/page_alloc.c:3954
 __alloc_frozen_pages_noprof+0x222/0x5b0 mm/page_alloc.c:5393
 alloc_slab_page mm/slub.c:3295 [inline]
 allocate_slab+0x7c/0x5e0 mm/slub.c:3410
 new_slab mm/slub.c:3456 [inline]
 refill_objects+0x2d8/0x350 mm/slub.c:7313
 refill_sheaf mm/slub.c:2833 [inline]
 __pcs_replace_empty_main+0x330/0x690 mm/slub.c:4699
 alloc_from_pcs mm/slub.c:4775 [inline]
 slab_alloc_node mm/slub.c:4909 [inline]
 __do_kmalloc_node mm/slub.c:5338 [inline]
 __kmalloc_node_track_caller_noprof+0x616/0x7b0 mm/slub.c:5468
 kmalloc_reserve net/core/skbuff.c:637 [inline]
 __alloc_skb+0x2bd/0x7a0 net/core/skbuff.c:715
 alloc_skb include/linux/skbuff.h:1384 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:819 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:876 [inline]
 nsim_dev_trap_report_work+0x2b1/0xcb0 drivers/net/netdevsim/dev.c:922
 process_one_work+0xaaf/0x1480 kernel/workqueue.c:3379
 process_scheduled_works kernel/workqueue.c:3462 [inline]
 worker_thread+0xb05/0x10d0 kernel/workqueue.c:3543
 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
page last free pid 1504 tgid 1504 ts 207023209551 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1417 [inline]
 free_unref_folios+0xd50/0x1a20 mm/page_alloc.c:3022
 folios_put_refs+0x815/0x920 mm/folio.c:1055
 release_pages+0x464/0x4d0 mm/folio.c:1095
 io_free_region+0xb3/0x240 io_uring/memmap.c:102
 io_rings_free io_uring/io_uring.c:2083 [inline]
 io_ring_ctx_free+0x2de/0x610 io_uring/io_uring.c:2191
 io_ring_exit_work+0x908/0x990 io_uring/io_uring.c:2421
 process_one_work+0xaaf/0x1480 kernel/workqueue.c:3379
 process_scheduled_works kernel/workqueue.c:3462 [inline]
 worker_thread+0xb05/0x10d0 kernel/workqueue.c:3543
 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:
 ffff88806afe0080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88806afe0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88806afe0180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88806afe0200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88806afe0280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================



	

	



	Crashes (2):
		
		

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			2026/07/11 17:52
			linux-next
			bee763d5f341
			d78ea535
			.config
			console log
			report
			
			
			info
			
				[disk image]
			
				[vmlinux]
			
				[kernel image]
			
			ci-upstream-rust-kasan-gce
			KASAN: slab-use-after-free Read in skb_dequeue
		

		
		

			2026/05/15 08:47
			linux-next
			e98d21c170b0
			9cd3beaa
			.config
			console log
			report
			
			
			info
			
				[disk image]
			
				[vmlinux]
			
				[kernel image]
			
			ci-upstream-rust-kasan-gce
			KASAN: slab-use-after-free Read in skb_dequeue
		

		
		


* Struck through repros no longer work on HEAD.