KASAN: use-after-free Read in atime_needs_update

Status: upstream: reported C repro on 2026/06/15 11:14
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+21e628b7ec5ec914f73a@syzkaller.appspotmail.com
First crash: 50d, last: 18d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/08/03 lts (merge base) 228da13e907e C [report] KASAN: use-after-free Read in pick_link
2026/08/03 upstream (ToT) 075b74841bd0 C Didn't crash
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-15 KASAN: use-after-free Read in atime_needs_update origin:upstream 19 syz, C 3 6d02h 69d 0/2 upstream: reported C repro on 2026/05/27 09:52
android-6-12 KASAN: slab-use-after-free Read in atime_needs_update origin:upstream 19 syz, C 1 83d 172d 0/1 premoderation: reported C repro on 2026/02/12 18:58
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/07/06 03:43 15m retest repro android14-6.1 log
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/07/16 12:10 3h13m bisect fix android14-6.1 OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in atime_needs_update+0x74b/0x810 fs/inode.c:1988
Read of size 4 at addr ffff8881329aed8c by task syz.1.2188/6912

CPU: 1 PID: 6912 Comm: syz.1.2188 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x71/0x200 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:420
 kasan_report+0x122/0x150 mm/kasan/report.c:524
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350
 atime_needs_update+0x74b/0x810 fs/inode.c:1988
 pick_link+0x496/0xe30 fs/namei.c:1788
 step_into+0xc27/0xf00 fs/namei.c:1875
 walk_component fs/namei.c:2011 [inline]
 link_path_walk+0x744/0xeb0 fs/namei.c:2332
 path_parentat fs/namei.c:2533 [inline]
 __filename_parentat+0x22d/0x650 fs/namei.c:2557
 filename_parentat fs/namei.c:2575 [inline]
 do_unlinkat+0xeb/0x6c0 fs/namei.c:4368
 __do_sys_unlinkat fs/namei.c:4440 [inline]
 __se_sys_unlinkat fs/namei.c:4433 [inline]
 __x64_sys_unlinkat+0xd8/0xf0 fs/namei.c:4433
 x64_sys_call+0x79f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:264
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f3c8ef9ce59
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:00007f3c8ff07028 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 00007f3c8f215fa0 RCX: 00007f3c8ef9ce59
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000000000000004
RBP: 00007f3c8f032d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3c8f216038 R14: 00007f3c8f215fa0 R15: 00007fffc5e4b388
 </TASK>

Allocated by task 6912:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505
 __kasan_slab_alloc+0x72/0x80 mm/kasan/common.c:334
 kasan_slab_alloc include/linux/kasan.h:202 [inline]
 slab_post_alloc_hook+0x4f/0x2d0 mm/slab.h:768
 slab_alloc_node mm/slub.c:3382 [inline]
 slab_alloc mm/slub.c:3392 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3399 [inline]
 kmem_cache_alloc_lru+0x104/0x280 mm/slub.c:3415
 alloc_inode_sb include/linux/fs.h:3263 [inline]
 alloc_inode fs/inode.c:266 [inline]
 new_inode_pseudo+0x8f/0x1f0 fs/inode.c:1074
 new_inode+0x28/0x1e0 fs/inode.c:1102
 bpf_get_inode kernel/bpf/inode.c:116 [inline]
 bpf_symlink+0x65/0x270 kernel/bpf/inode.c:394
 vfs_symlink+0x261/0x3f0 fs/namei.c:4478
 do_symlinkat+0x24a/0x5d0 fs/namei.c:4507
 __do_sys_symlinkat fs/namei.c:4524 [inline]
 __se_sys_symlinkat fs/namei.c:4521 [inline]
 __x64_sys_symlinkat+0x99/0xb0 fs/namei.c:4521
 x64_sys_call+0x282/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:267
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 6919:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x132/0x180 mm/kasan/common.c:242
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:250
 kasan_slab_free include/linux/kasan.h:178 [inline]
 slab_free_hook mm/slub.c:1750 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1776
 slab_free mm/slub.c:3712 [inline]
 kmem_cache_free+0x12d/0x300 mm/slub.c:3737
 free_inode_nonrcu+0x1c/0x20 fs/inode.c:245
 bpf_destroy_inode+0x14a/0x170 kernel/bpf/inode.c:621
 destroy_inode fs/inode.c:314 [inline]
 evict+0x7ac/0x8c0 fs/inode.c:724
 iput_final fs/inode.c:1845 [inline]
 iput+0x633/0x690 fs/inode.c:1871
 do_unlinkat+0x380/0x6c0 fs/namei.c:4404
 __do_sys_unlinkat fs/namei.c:4440 [inline]
 __se_sys_unlinkat fs/namei.c:4433 [inline]
 __x64_sys_unlinkat+0xd8/0xf0 fs/namei.c:4433
 x64_sys_call+0x79f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:264
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff8881329aed80
 which belongs to the cache inode_cache of size 704
The buggy address is located 12 bytes inside of
 704-byte region [ffff8881329aed80, ffff8881329af040)

The buggy address belongs to the physical page:
page:ffffea0004ca6b00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8881329ae700 pfn:0x1329ac
head:ffffea0004ca6b00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004ca1d00 dead000000000002 ffff8881001ed200
raw: ffff8881329ae700 000000008013000f 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Reclaimable, gfp_mask 0x1d20d0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 885, tgid 883 (syz.6.179), ts 73986658359, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2672
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2679
 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4586
 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5930
 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
 allocate_slab mm/slub.c:1967 [inline]
 new_slab+0x98/0x3e0 mm/slub.c:2020
 ___slab_alloc+0x70f/0xb70 mm/slub.c:3177
 __slab_alloc+0x5e/0xa0 mm/slub.c:3263
 slab_alloc_node mm/slub.c:3348 [inline]
 slab_alloc mm/slub.c:3392 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3399 [inline]
 kmem_cache_alloc_lru+0x144/0x280 mm/slub.c:3415
 alloc_inode_sb include/linux/fs.h:3263 [inline]
 alloc_inode fs/inode.c:266 [inline]
 new_inode_pseudo+0x8f/0x1f0 fs/inode.c:1074
 new_inode+0x28/0x1e0 fs/inode.c:1102
 simple_fill_super+0xd1/0x5c0 fs/libfs.c:658
 bpf_fill_super+0xb0/0x700 kernel/bpf/inode.c:750
 vfs_get_super fs/super.c:1216 [inline]
 get_tree_nodev+0xc4/0x170 fs/super.c:1246
 bpf_get_tree+0x1c/0x20 kernel/bpf/inode.c:766
 vfs_get_tree+0x9a/0x270 fs/super.c:1578
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881329aec80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881329aed00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881329aed80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff8881329aee00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881329aee80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/15 11:13 android14-6.1 f17c14b8ada7 1d2f3589 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in atime_needs_update
* Struck through repros no longer work on HEAD.