KASAN: use-after-free Read in pick_link

Status: upstream: reported C repro on 2026/02/22 08:05
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+6c9d52b3009b181a9d1c@syzkaller.appspotmail.com
First crash: 152d, last: 9d10h
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/02/22 lts (merge base) e50b81c50fcb C [report] KASAN: use-after-free Read in pick_link
2026/02/22 upstream (ToT) 32a92f8c8932 C [report] KASAN: slab-out-of-bounds Read in link_path_walk
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-15 KASAN: use-after-free Read in pick_link 19 1 4d00h 4d00h 0/2 premoderation: reported on 2026/07/20 09:03
upstream general protection fault in pick_link (2) ntfs3 2 C error 7 387d 402d 29/29 fixed on 2025/09/04 16:57
android-6-12 KASAN: slab-use-after-free Read in pick_link origin:upstream 19 C 4 113d 161d 0/1 premoderation: reported C repro on 2026/02/12 18:21
upstream KMSAN: uninit-value in pick_link squashfs 7 C 9 718d 723d 28/29 fixed on 2024/10/03 15:25
upstream KMSAN: kernel-infoleak in _copy_to_iter (8) mm 21 C 21180 1141d 1236d 22/29 fixed on 2023/06/08 14:41
upstream general protection fault in pick_link ntfs3 2 C 5 466d 616d 28/29 fixed on 2025/05/06 15:33
linux-6.6 general protection fault in pick_link origin:upstream 2 C done 2 348d 348d 2/2 fixed on 2025/09/19 10:03
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2026/06/11 15:28 20m retest repro android14-6.1 log
2026/03/08 11:50 11m retest repro android14-6.1 report log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in pick_link+0x567/0xe30 fs/namei.c:1799
Read of size 8 at addr ffff888123abd610 by task syz.4.105/781

CPU: 1 PID: 781 Comm: syz.4.105 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:351
 pick_link+0x567/0xe30 fs/namei.c:1799
 step_into+0xc5c/0xf40 fs/namei.c:1875
 walk_component fs/namei.c:2011 [inline]
 link_path_walk+0x6c1/0xe80 fs/namei.c:2332
 path_openat+0x27c/0x2f80 fs/namei.c:3786
 do_filp_open+0x1f1/0x430 fs/namei.c:3817
 do_sys_openat2+0x15e/0x810 fs/open.c:1343
 do_sys_open fs/open.c:1359 [inline]
 __do_sys_openat fs/open.c:1375 [inline]
 __se_sys_openat fs/open.c:1370 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1370
 x64_sys_call+0x783/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:258
 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: 0033:0x7f4837b9c629
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:00007f48379bd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f4837e16180 RCX: 00007f4837b9c629
RDX: 0000000000008000 RSI: 0000200000000180 RDI: 0000000000000005
RBP: 00007f4837c32b39 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000004d R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4837e16218 R14: 00007f4837e16180 R15: 00007ffd14571258
 </TASK>

Allocated by task 781:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_alloc_info+0x25/0x30 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:1073
 new_inode+0x28/0x1e0 fs/inode.c:1101
 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+0x124/0x5a0 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 777:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x31/0x50 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+0x7d0/0x8f0 fs/inode.c:723
 iput_final fs/inode.c:1844 [inline]
 iput+0x620/0x670 fs/inode.c:1870
 do_unlinkat+0x380/0x6d0 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 ffff888123abd380
 which belongs to the cache inode_cache of size 704
The buggy address is located 656 bytes inside of
 704-byte region [ffff888123abd380, ffff888123abd640)

The buggy address belongs to the physical page:
page:ffffea00048eaf00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x123abc
head:ffffea00048eaf00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 ffffea00045c5c00 dead000000000003 ffff8881001ed380
raw: 0000000000000000 0000000080130013 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 289, tgid 289 (syz-executor), ts 86704235187, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2643
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2650
 get_page_from_freelist+0x2d12/0x2d80 mm/page_alloc.c:4554
 __alloc_pages+0x1d9/0x480 mm/page_alloc.c:5868
 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
 allocate_slab mm/slub.c:1967 [inline]
 new_slab+0x98/0x3d0 mm/slub.c:2020
 ___slab_alloc+0x6bd/0xb20 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:1073
 get_pipe_inode fs/pipe.c:878 [inline]
 create_pipe_files+0x4f/0x6c0 fs/pipe.c:918
 __do_pipe_flags+0x4f/0x200 fs/pipe.c:967
 do_pipe2+0xa7/0x190 fs/pipe.c:1015
 __do_sys_pipe2 fs/pipe.c:1033 [inline]
 __se_sys_pipe2 fs/pipe.c:1031 [inline]
 __x64_sys_pipe2+0x5a/0x70 fs/pipe.c:1031
 x64_sys_call+0x258/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:294
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888123abd500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888123abd580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888123abd600: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                         ^
 ffff888123abd680: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
 ffff888123abd700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/22 07:55 android14-6.1 8494a7f300cc 6e7b5511 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in pick_link
2026/07/14 22:53 android14-6.1 e69716042404 2130f682 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in pick_link
2026/05/24 09:55 android14-6.1 108b53924ea3 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in pick_link
2026/05/24 02:03 android14-6.1 108b53924ea3 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in pick_link
2026/02/22 06:06 android14-6.1 8494a7f300cc 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in pick_link
* Struck through repros no longer work on HEAD.