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

Status: upstream: reported on 2026/01/21 08:28
Subsystems: fs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+e8b3520b53e78e90034e@syzkaller.appspotmail.com
First crash: 192d, last: 48d
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision Error
a1886148 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ✅ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in proc_invalidate_siblings_dcache (2) 2026/05/31 05:52 2026/05/31 05:52 2026/05/31 06:43 6b4a8443 

			
				
	

	
	

		4792bef1
		assessment-security
		
			
		
		💥
		KASAN: slab-use-after-free Read in proc_invalidate_siblings_dcache (2)
		2026/05/14 14:18
		2026/05/14 14:18
		2026/05/14 14:19
		6ccb967e
		
			
failed to run ["git" "pull" "origin" "HEAD" "--depth=1" "--allow-unrelated-histories"]: exit status 128
From /app/workdir/repo/linux
 * branch                HEAD       -> FETCH_HEAD
Updating files:  ...

			
				
truncated to first 200 bytes; open job for full error

			
				
	

	
	

		6bb0a4d8
		repro
		
			
				
			
				
			
				
			
		
		❓
		KASAN: slab-use-after-free Read in proc_invalidate_siblings_dcache (2)
		2026/03/06 20:43
		2026/03/06 20:43
		2026/03/06 20:51
		31e9c887
		
			

			
				
	

	
	



			

		

	

	
	

		

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			[syzbot] [fs?] KASAN: slab-use-after-free Read in proc_invalidate_siblings_dcache (2)
			0 (1)
			2026/01/21 08:28
		

	
	




			
			
		

	

	
	

		

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			Similar bugs (2)
		

		

			




	
	

		
			Kernel
		
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			upstream
			
				KASAN: slab-use-after-free Read in proc_invalidate_siblings_dcache
					fs
			
			19
			
			
			
			1
			317d
			
				
					313d
				
			
			
			
			
				0/29
			
			
				
					
						auto-obsoleted due to no activity on 2025/12/23 02:53
					
				
			
			
		

	
		

			upstream
			
				general protection fault in proc_invalidate_siblings_dcache
					fs
			
			2
			
			
			
			1
			1813d
			
				
					1809d
				
			
			
			
			
				0/29
			
			
				
					
						auto-closed as invalid on 2021/11/08 05:37
					
				
			
			
		

	
	





			
			
			
			
		

	

	

	
	
Sample crash report:

	
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3f) already exists on: ipvlan2
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
batman_adv: batadv0: Interface activated: ipvlan3
==================================================================
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 ffff8880621d8e90 by task syz.1.718/8477

CPU: 0 UID: 0 PID: 8477 Comm: syz.1.718 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
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
 rt_mutex_slowunlock+0xbf/0x8b0 kernel/locking/rtmutex.c:1426
 proc_invalidate_siblings_dcache+0x3db/0x6c0 fs/proc/inode.c:143
 release_task+0x1207/0x16f0 kernel/exit.c:291
 exit_notify kernel/exit.c:777 [inline]
 do_exit+0x1674/0x22c0 kernel/exit.c:988
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1119
 get_signal+0x1284/0x1330 kernel/signal.c:3038
 arch_do_signal_or_restart+0xbc/0x840 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0xa9/0x680 kernel/entry/common.c:98
 __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
RIP: 0033:0x7facd8e0ce59
Code: Unable to access opcode bytes at 0x7facd8e0ce2f.
RSP: 002b:00007facd70240e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007facd9086188 RCX: 00007facd8e0ce59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007facd9086188
RBP: 00007facd9086180 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007facd9086218 R14: 00007ffd573e0480 R15: 00007ffd573e0568
 </TASK>

Allocated by task 8477:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4570 [inline]
 slab_alloc_node mm/slub.c:4899 [inline]
 kmem_cache_alloc_lru_noprof+0x33c/0x680 mm/slub.c:4918
 __d_alloc+0x37/0x6f0 fs/dcache.c:1807
 d_alloc_parallel+0xe6/0x1610 fs/dcache.c:2671
 __lookup_slow+0x152/0x440 fs/namei.c:1900
 lookup_slow+0x53/0x70 fs/namei.c:1932
 walk_component fs/namei.c:2278 [inline]
 link_path_walk+0x1273/0x18d0 fs/namei.c:2649
 path_openat+0x2d5/0x38a0 fs/namei.c:4854
 do_file_open+0x23e/0x4a0 fs/namei.c:4887
 do_sys_openat2+0x113/0x200 fs/open.c:1364
 do_sys_open fs/open.c:1370 [inline]
 __do_sys_openat fs/open.c:1386 [inline]
 __se_sys_openat fs/open.c:1381 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1381
 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 28:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 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:2689 [inline]
 slab_free mm/slub.c:6251 [inline]
 kmem_cache_free+0x187/0x6c0 mm/slub.c:6378
 rcu_do_batch kernel/rcu/tree.c:2617 [inline]
 rcu_core kernel/rcu/tree.c:2869 [inline]
 rcu_cpu_kthread+0x99e/0x1470 kernel/rcu/tree.c:2957
 smpboot_thread_fn+0x541/0xa50 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

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
 __call_rcu_common kernel/rcu/tree.c:3131 [inline]
 call_rcu+0xee/0x890 kernel/rcu/tree.c:3251
 __dentry_kill+0x4a9/0x690 fs/dcache.c:737
 shrink_kill+0xa9/0x2c0 fs/dcache.c:1195
 shrink_dentry_list+0x2e3/0x5e0 fs/dcache.c:1222
 shrink_dcache_tree+0xe9/0x5d0 fs/dcache.c:-1
 shrink_dcache_parent fs/dcache.c:1693 [inline]
 d_invalidate+0xde/0x210 fs/dcache.c:1775
 proc_invalidate_siblings_dcache+0x3d3/0x6c0 fs/proc/inode.c:142
 release_task+0x1207/0x16f0 kernel/exit.c:291
 wait_task_zombie kernel/exit.c:1281 [inline]
 wait_consider_task+0x1966/0x2e30 kernel/exit.c:1508
 do_wait_thread kernel/exit.c:1571 [inline]
 __do_wait+0x155/0x740 kernel/exit.c:1689
 do_wait+0x1e7/0x510 kernel/exit.c:1723
 kernel_wait4+0x232/0x2b0 kernel/exit.c:1882
 __do_sys_wait4 kernel/exit.c:1910 [inline]
 __se_sys_wait4 kernel/exit.c:1906 [inline]
 __x64_sys_wait4+0x166/0x240 kernel/exit.c:1906
 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

The buggy address belongs to the object at ffff8880621d8dc0
 which belongs to the cache dentry of size 376
The buggy address is located 208 bytes inside of
 freed 376-byte region [ffff8880621d8dc0, ffff8880621d8f38)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff8880621d8898 pfn:0x621d8
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff8880621d9ef1
flags: 0x80000000000240(workingset|head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000240 ffff88801b6e13c0 ffffea00017f6990 ffffea0000f5d110
raw: ffff8880621d8898 0000000800120010 00000000f5000000 ffff8880621d9ef1
head: 0080000000000240 ffff88801b6e13c0 ffffea00017f6990 ffffea0000f5d110
head: ffff8880621d8898 0000000800120010 00000000f5000000 ffff8880621d9ef1
head: 0080000000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Reclaimable, gfp_mask 0xd20d0(__GFP_RECLAIMABLE|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5610, tgid 5610 (syz-executor), ts 140470420342, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1853
 prep_new_page mm/page_alloc.c:1861 [inline]
 get_page_from_freelist+0x28b2/0x2930 mm/page_alloc.c:3941
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5221
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab+0x77/0x660 mm/slub.c:3467
 new_slab mm/slub.c:3525 [inline]
 refill_objects+0x33c/0x3d0 mm/slub.c:7272
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x373/0x720 mm/slub.c:4652
 alloc_from_pcs mm/slub.c:4750 [inline]
 slab_alloc_node mm/slub.c:4884 [inline]
 kmem_cache_alloc_lru_noprof+0x433/0x680 mm/slub.c:4918
 __d_alloc+0x37/0x6f0 fs/dcache.c:1807
 d_alloc+0x4b/0x190 fs/dcache.c:1886
 lookup_one_qstr_excl+0xd8/0x360 fs/namei.c:1801
 __start_dirop fs/namei.c:2916 [inline]
 start_dirop fs/namei.c:2938 [inline]
 filename_create+0x20e/0x370 fs/namei.c:4950
 filename_mkdirat+0xd2/0x520 fs/namei.c:5297
 __do_sys_mkdirat fs/namei.c:5325 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5322
 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
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8880621d8d80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff8880621d8e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880621d8e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8880621d8f00: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fa
 ffff8880621d8f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================



	

	



	Crashes (4):
		
		

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			2026/06/10 19:17
			upstream
			acb7500801e9
			f79bac11
			.config
			console log
			report
			
			
			info
			
				[disk image]
			
				[vmlinux]
			
				[kernel image]
			
			ci-upstream-kasan-gce-smack-root
			KASAN: slab-use-after-free Read in proc_invalidate_siblings_dcache
		

		
		

			2026/05/17 06:28
			upstream
			6916d5703ddf
			de5aae85
			.config
			console log
			report
			
			
			info
			
				[disk image]
			
				[vmlinux]
			
				[kernel image]
			
			ci-upstream-kasan-gce-smack-root
			KASAN: slab-use-after-free Read in proc_invalidate_siblings_dcache
		

		
		

			2026/02/16 05:44
			git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git for-next
			18be4ca5cb4e
			1e62d198
			.config
			console log
			report
			
			
			
			
				[disk image (non-bootable)]
			
				[vmlinux]
			
				[kernel image]
			
			ci-qemu2-riscv64
			KASAN: slab-use-after-free Read in proc_invalidate_siblings_dcache
		

		
		

			2026/01/17 03:35
			git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git for-next
			8f0b4cce4481
			56f88057
			.config
			console log
			report
			
			
			
			
				[disk image (non-bootable)]
			
				[vmlinux]
			
				[kernel image]
			
			ci-qemu2-riscv64
			KASAN: slab-use-after-free Read in proc_invalidate_siblings_dcache
		

		
		


* Struck through repros no longer work on HEAD.