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

Status: upstream: reported C repro on 2026/07/28 14:15
Subsystems: fs
Labels: prio:normal
[Documentation on labels]
Reported-by: syzbot+8358d1f3d9c15bdf1c9a@syzkaller.appspotmail.com
First crash: 10d, last: 1d01h
✨ AI Patch Versions (1)
Version Stage Reported Report Link Job
1 moderation 2026/07/29 11:04 Discussion 13fec684-23f7-4f06-99db-ed37ae92a405
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
13fec684 patching KASAN: slab-use-after-free Read in configfs_dirent_is_ready 2026/07/29 08:36 2026/07/29 08:36 2026/07/29 11:04 19622d9d

			
		
b06aefe9 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ KASAN: slab-use-after-free Read in configfs_dirent_is_ready 2026/07/26 00:00 2026/07/26 00:00 2026/07/26 00:50 492bab15

			
		
Discussions (3)
Title Replies (including bot) Last reply
[PATCH v2] configfs: fix race between symlink and rmdir 1 (1) 2026/07/30 09:20
[PATCH] configfs: fix race between symlink and rmdir 3 (3) 2026/07/30 09:05
[syzbot] [fs?] KASAN: slab-use-after-free Read in configfs_dirent_is_ready 0 (1) 2026/07/28 14:15

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in configfs_dirent_is_ready+0x6d/0x70 fs/configfs/dir.c:363
Read of size 4 at addr ffff88804750d8b8 by task syz-executor315/5666

CPU: 1 UID: 0 PID: 5666 Comm: syz-executor315 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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
 configfs_dirent_is_ready+0x6d/0x70 fs/configfs/dir.c:363
 create_link fs/configfs/symlink.c:85 [inline]
 configfs_symlink+0x616/0x1030 fs/configfs/symlink.c:199
 vfs_symlink+0x18b/0x330 fs/namei.c:5654
 filename_symlinkat+0x1cd/0x420 fs/namei.c:5679
 __do_sys_symlinkat fs/namei.c:5699 [inline]
 __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5694
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe255ccbd19
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 d0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdade2b528 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fe255ccbd19
RDX: 0000200000000340 RSI: 00000000ffffff9c RDI: 0000200000000300
RBP: 0000000000000000 R08: 000055556f6b9780 R09: 000055556f6b9780
R10: 000055556f6b9780 R11: 0000000000000246 R12: 00007ffdade2b548
R13: 00007ffdade2b560 R14: 00007ffdade2b5a0 R15: 0000000000000002
 </TASK>

Allocated by task 5665:
 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:4608 [inline]
 slab_alloc_node mm/slub.c:4921 [inline]
 kmem_cache_alloc_noprof+0x358/0x680 mm/slub.c:4935
 configfs_new_dirent+0x59/0x470 fs/configfs/dir.c:193
 configfs_make_dirent fs/configfs/dir.c:259 [inline]
 configfs_create_dir fs/configfs/dir.c:304 [inline]
 configfs_attach_item+0xa1/0xd60 fs/configfs/dir.c:863
 configfs_attach_group+0x2a/0x370 fs/configfs/dir.c:898
 configfs_mkdir+0x6f0/0x9e0 fs/configfs/dir.c:1423
 vfs_mkdir+0x408/0x620 fs/namei.c:5270
 filename_mkdirat+0x289/0x520 fs/namei.c:5303
 __do_sys_mkdirat fs/namei.c:5324 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5321
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5665:
 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:6388 [inline]
 kmem_cache_free+0x187/0x6c0 mm/slub.c:6515
 release_configfs_dirent fs/configfs/configfs_internal.h:139 [inline]
 configfs_put fs/configfs/configfs_internal.h:156 [inline]
 configfs_d_iput+0x209/0x270 fs/configfs/dir.c:63
 d_delete_notify include/linux/fsnotify.h:379 [inline]
 vfs_rmdir+0x24a/0x6b0 fs/namei.c:5388
 filename_rmdir+0x292/0x520 fs/namei.c:5432
 __do_sys_unlinkat fs/namei.c:5607 [inline]
 __se_sys_unlinkat+0x71/0x1a0 fs/namei.c:5600
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88804750d880
 which belongs to the cache configfs_dir_cache of size 96
The buggy address is located 56 bytes inside of
 freed 96-byte region [ffff88804750d880, ffff88804750d8e0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4750d
flags: 0x80000000000000(node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000000 ffff888140419500 dead000000000122 0000000000000000
raw: 0000000000000000 0000000800200020 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5663, tgid 5663 (syz-executor315), ts 163911028012
 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+0x264c/0x26c0 mm/page_alloc.c:3955
 __alloc_frozen_pages_noprof+0x222/0x5b0 mm/page_alloc.c:5394
 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:7321
 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]
 kmem_cache_alloc_noprof+0x455/0x680 mm/slub.c:4935
 configfs_new_dirent+0x59/0x470 fs/configfs/dir.c:193
 configfs_make_dirent+0x35/0x160 fs/configfs/dir.c:259
 configfs_create_file+0xe3/0x130 fs/configfs/file.c:454
 populate_attrs fs/configfs/dir.c:640 [inline]
 configfs_attach_item+0x8df/0xd60 fs/configfs/dir.c:865
 configfs_attach_group+0x2a/0x370 fs/configfs/dir.c:898
 configfs_mkdir+0x6f0/0x9e0 fs/configfs/dir.c:1423
 vfs_mkdir+0x408/0x620 fs/namei.c:5270
 filename_mkdirat+0x289/0x520 fs/namei.c:5303
 __do_sys_mkdirat fs/namei.c:5324 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5321
page last free pid 29 tgid 29 ts 163672667164 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0x1185/0x1270 mm/page_alloc.c:2962
 __tlb_remove_table_free mm/mmu_gather.c:228 [inline]
 tlb_remove_table_rcu+0x85/0x100 mm/mmu_gather.c:291
 rcu_do_batch kernel/rcu/tree.c:2645 [inline]
 rcu_core kernel/rcu/tree.c:2897 [inline]
 rcu_cpu_kthread+0x950/0x1480 kernel/rcu/tree.c:2985
 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

Memory state around the buggy address:
 ffff88804750d780: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff88804750d800: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff88804750d880: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                        ^
 ffff88804750d900: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff88804750d980: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/02 17:44 linux-next cc2b5f627e8c e611ffe1 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in configfs_dirent_is_ready
2026/07/27 03:03 linux-next cc2b5f627e8c 492bab15 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Read in configfs_dirent_is_ready
2026/08/01 19:18 upstream 0131b508c0e2 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in configfs_dirent_is_ready
2026/07/28 07:25 upstream 62cc90241548 45ae1df4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root KASAN: slab-use-after-free Read in configfs_dirent_is_ready
2026/07/24 14:10 upstream d326f83e819c 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root KASAN: slab-use-after-free Read in configfs_dirent_is_ready
2026/07/29 19:45 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 configfs_dirent_is_ready
* Struck through repros no longer work on HEAD.