KASAN: use-after-free Read in atime_needs_update

Status: upstream: reported C repro on 2026/05/27 09:52
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+8d57d64702ce53fbe343@syzkaller.appspotmail.com
First crash: 59d, last: 26d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/05/31 lts (merge base) 93741761e5e3 C [report] lost connection to test machine
2026/05/31 upstream (ToT) 174914ea5513 C [report] lost connection to test machine
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 KASAN: use-after-free Read in atime_needs_update 19 C 1 9d00h 40d 0/2 upstream: reported C repro on 2026/06/15 11:14
android-6-12 KASAN: slab-use-after-free Read in atime_needs_update origin:upstream 19 C 1 73d 162d 0/1 premoderation: reported C repro on 2026/02/12 18:58
▶ ▼ Last patch testing requests (3)
Created Duration User Patch Repo Result
2026/07/18 08:38 15m retest repro android13-5.15-lts log
2026/07/18 08:38 15m retest repro android13-5.15-lts log
2026/06/20 19:00 12m retest repro android13-5.15-lts log
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/06/26 17:34 1h51m bisect fix android13-5.15-lts OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in atime_needs_update+0x74b/0x810 fs/inode.c:1922
Read of size 4 at addr ffff88812d963a7c by task syz.2.16030/16088

CPU: 0 PID: 16088 Comm: syz.2.16030 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x10f/0x150 mm/kasan/report.c:444
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 atime_needs_update+0x74b/0x810 fs/inode.c:1922
 pick_link+0x4b3/0xe00 fs/namei.c:1762
 step_into+0xac8/0xce0 fs/namei.c:1840
 walk_component+0x263/0x460 fs/namei.c:1990
 link_path_walk+0x688/0xde0 fs/namei.c:-1
 path_parentat fs/namei.c:2510 [inline]
 __filename_parentat+0x254/0x690 fs/namei.c:2534
 filename_parentat fs/namei.c:2552 [inline]
 do_unlinkat+0xeb/0x6c0 fs/namei.c:4327
 __do_sys_unlinkat fs/namei.c:4399 [inline]
 __se_sys_unlinkat fs/namei.c:4392 [inline]
 __x64_sys_unlinkat+0xd8/0xf0 fs/namei.c:4392
 x64_sys_call+0x4c0/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:264
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f3bf51f9e59
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:00007f3bf505c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 00007f3bf5472fa0 RCX: 00007f3bf51f9e59
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000000000000004
RBP: 00007f3bf528fe6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3bf5473038 R14: 00007f3bf5472fa0 R15: 00007ffc38863918
 </TASK>

Allocated by task 16088:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:433 [inline]
 __kasan_slab_alloc+0xb7/0xe0 mm/kasan/common.c:466
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3245 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
 alloc_inode fs/inode.c:266 [inline]
 new_inode_pseudo+0x7a/0x210 fs/inode.c:1011
 new_inode+0x28/0x1e0 fs/inode.c:1040
 bpf_get_inode kernel/bpf/inode.c:116 [inline]
 bpf_symlink+0x65/0x270 kernel/bpf/inode.c:394
 vfs_symlink+0x29e/0x470 fs/namei.c:4437
 do_symlinkat+0x24a/0x5d0 fs/namei.c:4466
 __do_sys_symlinkat fs/namei.c:4483 [inline]
 __se_sys_symlinkat fs/namei.c:4480 [inline]
 __x64_sys_symlinkat+0x99/0xb0 fs/namei.c:4480
 x64_sys_call+0x74b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:267
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 16089:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1728 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
 slab_free mm/slub.c:3526 [inline]
 kmem_cache_free+0x100/0x320 mm/slub.c:3544
 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+0x790/0x8b0 fs/inode.c:665
 iput_final fs/inode.c:1779 [inline]
 iput+0x651/0x7e0 fs/inode.c:1805
 do_unlinkat+0x380/0x6c0 fs/namei.c:4363
 __do_sys_unlinkat fs/namei.c:4399 [inline]
 __se_sys_unlinkat fs/namei.c:4392 [inline]
 __x64_sys_unlinkat+0xd8/0xf0 fs/namei.c:4392
 x64_sys_call+0x4c0/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:264
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff88812d963a70
 which belongs to the cache inode_cache of size 752
The buggy address is located 12 bytes inside of
 752-byte region [ffff88812d963a70, ffff88812d963d60)
The buggy address belongs to the page:
page:ffffea0004b65800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12d960
head:ffffea0004b65800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea0004b61d00 0000000900000009 ffff8881001c5500
raw: 0000000000000000 0000000080120012 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 3476, ts 396555112568, free_ts 394364335214
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
 get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa0/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x3ac/0x840 mm/slub.c:3033
 __slab_alloc+0x49/0x90 mm/slub.c:3120
 slab_alloc_node mm/slub.c:3211 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0x138/0x260 mm/slub.c:3260
 alloc_inode fs/inode.c:266 [inline]
 new_inode_pseudo+0x7a/0x210 fs/inode.c:1011
 new_inode+0x28/0x1e0 fs/inode.c:1040
 simple_fill_super+0xd1/0x5c0 fs/libfs.c:630
 bpf_fill_super+0xb1/0x790 kernel/bpf/inode.c:769
 vfs_get_super fs/super.c:1172 [inline]
 get_tree_nodev+0xb3/0x160 fs/super.c:1202
 bpf_get_tree+0x1c/0x20 kernel/bpf/inode.c:785
 vfs_get_tree+0x89/0x260 fs/super.c:1530
 vfs_fsconfig_locked+0x236/0x3f0 fs/fsopen.c:238
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1474 [inline]
 free_pcp_prepare mm/page_alloc.c:1546 [inline]
 free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3536
 free_unref_page+0xae/0x540 mm/page_alloc.c:3618
 free_the_page mm/page_alloc.c:805 [inline]
 __free_pages+0x6c/0x100 mm/page_alloc.c:5900
 __free_slab+0xe5/0x1e0 mm/slub.c:2025
 free_slab mm/slub.c:2040 [inline]
 discard_slab mm/slub.c:2046 [inline]
 __unfreeze_partials+0x15a/0x190 mm/slub.c:2532
 put_cpu_partial+0xc6/0x120 mm/slub.c:2612
 __slab_free+0x1d4/0x290 mm/slub.c:3395
 do_slab_free mm/slub.c:3514 [inline]
 ___cache_free+0x104/0x120 mm/slub.c:3535
 qlink_free+0x4d/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:443
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3245 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
 getname_flags+0xba/0x510 fs/namei.c:138
 getname+0x19/0x20 fs/namei.c:217

Memory state around the buggy address:
 ffff88812d963900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88812d963980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
>ffff88812d963a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fa fb
                                                                ^
 ffff88812d963a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88812d963b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/29 01:05 android13-5.15-lts c85054db4618 fb92f11c .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in atime_needs_update
2026/06/28 21:51 android13-5.15-lts c85054db4618 fb92f11c .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in atime_needs_update
2026/05/27 09:51 android13-5.15-lts 8969ee93a483 2b01f00e .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in atime_needs_update
* Struck through repros no longer work on HEAD.