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

Status: premoderation: reported C repro on 2026/02/12 18:21
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+c1105d3434556fd47472@syzkaller.appspotmail.com
First crash: 6d05h, last: 6d03h
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/02/12 lts (merge base) 0bf1a02494c7 C [report] KASAN: slab-out-of-bounds Read in link_path_walk
2026/02/12 upstream (ToT) 582a1ef360a0 C [report] KASAN: slab-use-after-free Read in selinux_inode_follow_link
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream general protection fault in pick_link (2) ntfs3 2 C error 7 232d 246d 29/29 fixed on 2025/09/04 16:57
upstream KMSAN: uninit-value in pick_link squashfs 7 C 9 563d 567d 28/29 fixed on 2024/10/03 15:25
upstream KMSAN: kernel-infoleak in _copy_to_iter (8) mm 21 C 21180 986d 1080d 22/29 fixed on 2023/06/08 14:41
upstream general protection fault in pick_link ntfs3 2 C 5 311d 461d 28/29 fixed on 2025/05/06 15:33
linux-6.6 general protection fault in pick_link origin:upstream 2 C done 2 192d 192d 2/2 fixed on 2025/09/19 10:03

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in pick_link+0x4f0/0xe80 fs/namei.c:1855
Read of size 8 at addr ffff888133d39610 by task syz.2.8138/23722

CPU: 1 UID: 0 PID: 23722 Comm: syz.2.8138 Not tainted syzkaller #0 ecbc8af4db0b1e168e71992ad8df1de57efedc45
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 print_address_description+0x71/0x210 mm/kasan/report.c:377
 print_report+0x4a/0x70 mm/kasan/report.c:481
 kasan_report+0x162/0x1a0 mm/kasan/report.c:594
 __asan_report_load8_noabort+0x18/0x20 mm/kasan/report_generic.c:381
 pick_link+0x4f0/0xe80 fs/namei.c:1855
 step_into+0xc68/0xf60 fs/namei.c:1931
 walk_component fs/namei.c:2067 [inline]
 link_path_walk+0x753/0xec0 fs/namei.c:2426
 path_parentat fs/namei.c:2635 [inline]
 __filename_parentat+0x22a/0x650 fs/namei.c:2659
 filename_parentat fs/namei.c:2677 [inline]
 do_unlinkat+0xfe/0x5a0 fs/namei.c:4516
 __do_sys_unlinkat fs/namei.c:4584 [inline]
 __se_sys_unlinkat fs/namei.c:4577 [inline]
 __x64_sys_unlinkat+0xda/0xf0 fs/namei.c:4577
 x64_sys_call+0x2974/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:264
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f39ef59bf79
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:00007f39f03e9028 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 00007f39ef815fa0 RCX: 00007f39ef59bf79
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000000000000004
RBP: 00007f39ef6327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f39ef816038 R14: 00007f39ef815fa0 R15: 00007ffe9afb0878
 </TASK>

Allocated by task 23722:
 kasan_save_stack mm/kasan/common.c:49 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:70
 kasan_save_alloc_info+0x40/0x50 mm/kasan/generic.c:565
 unpoison_slab_object mm/kasan/common.c:321 [inline]
 __kasan_slab_alloc+0x73/0x90 mm/kasan/common.c:347
 kasan_slab_alloc include/linux/kasan.h:251 [inline]
 slab_post_alloc_hook mm/slub.c:4202 [inline]
 slab_alloc_node mm/slub.c:4251 [inline]
 kmem_cache_alloc_lru_noprof+0x1c2/0x410 mm/slub.c:4272
 alloc_inode+0xa9/0x270 fs/inode.c:271
 new_inode_pseudo fs/inode.c:1117 [inline]
 new_inode+0x25/0x1e0 fs/inode.c:1136
 bpf_get_inode kernel/bpf/inode.c:117 [inline]
 bpf_symlink+0x65/0x200 kernel/bpf/inode.c:392
 vfs_symlink+0x3ee/0x620 fs/namei.c:4623
 do_symlinkat+0x1ba/0x400 fs/namei.c:4649
 __do_sys_symlinkat fs/namei.c:4665 [inline]
 __se_sys_symlinkat fs/namei.c:4662 [inline]
 __x64_sys_symlinkat+0x99/0xb0 fs/namei.c:4662
 x64_sys_call+0x1f79/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:267
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 23724:
 kasan_save_stack mm/kasan/common.c:49 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:70
 kasan_save_free_info+0x4a/0x60 mm/kasan/generic.c:579
 poison_slab_object mm/kasan/common.c:249 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:266
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2445 [inline]
 slab_free mm/slub.c:4714 [inline]
 kmem_cache_free+0x1bd/0x4f0 mm/slub.c:4821
 free_inode_nonrcu+0x20/0x30 fs/inode.c:250
 bpf_destroy_inode+0x14e/0x180 kernel/bpf/inode.c:786
 destroy_inode fs/inode.c:319 [inline]
 evict+0x7f2/0xac0 fs/inode.c:762
 iput_final fs/inode.c:1890 [inline]
 iput+0x635/0x8d0 fs/inode.c:1916
 do_unlinkat+0x3d2/0x5a0 fs/namei.c:4548
 __do_sys_unlinkat fs/namei.c:4584 [inline]
 __se_sys_unlinkat fs/namei.c:4577 [inline]
 __x64_sys_unlinkat+0xda/0xf0 fs/namei.c:4577
 x64_sys_call+0x2974/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:264
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

The buggy address belongs to the object at ffff888133d39380
 which belongs to the cache inode_cache of size 704
The buggy address is located 656 bytes inside of
 freed 704-byte region [ffff888133d39380, ffff888133d39640)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x133d38
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x4000000000000040(head|zone=1)
page_type: f5(slab)
raw: 4000000000000040 ffff88810167f3c0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080130013 00000001f5000000 0000000000000000
head: 4000000000000040 ffff88810167f3c0 dead000000000122 0000000000000000
head: 0000000000000000 0000000080130013 00000001f5000000 0000000000000000
head: 4000000000000002 ffffea0004cf4e01 ffffffffffffffff 0000000000000000
head: 0000000000000004 0000000000000000 00000000ffffffff 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 23676, tgid 23669 (syz.5.8119), ts 76653418921, free_ts 75402296679
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook+0x3b8/0x3f0 mm/page_alloc.c:1826
 prep_new_page+0x1c/0x110 mm/page_alloc.c:1834
 get_page_from_freelist+0x496e/0x4a20 mm/page_alloc.c:3914
 __alloc_pages_noprof+0x35f/0x7e0 mm/page_alloc.c:5264
 alloc_slab_page+0x6b/0x1e0 mm/slub.c:-1
 allocate_slab+0x69/0x420 mm/slub.c:2687
 new_slab mm/slub.c:2741 [inline]
 ___slab_alloc+0x5a2/0x8d0 mm/slub.c:3934
 __slab_alloc mm/slub.c:4025 [inline]
 __slab_alloc_node mm/slub.c:4078 [inline]
 slab_alloc_node mm/slub.c:4239 [inline]
 kmem_cache_alloc_lru_noprof+0x295/0x410 mm/slub.c:4272
 alloc_inode+0xa9/0x270 fs/inode.c:271
 new_inode_pseudo fs/inode.c:1117 [inline]
 new_inode+0x25/0x1e0 fs/inode.c:1136
 simple_fill_super+0xee/0x700 fs/libfs.c:1003
 bpf_fill_super+0xf5/0xc90 kernel/bpf/inode.c:1021
 vfs_get_super fs/super.c:1283 [inline]
 get_tree_nodev+0xcb/0x170 fs/super.c:1302
 bpf_get_tree+0x20/0x30 kernel/bpf/inode.c:1039
 vfs_get_tree+0xa1/0x290 fs/super.c:1817
 vfs_cmd_create+0xb0/0x220 fs/fsopen.c:231
page last free pid 22924 tgid 22924 stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1352 [inline]
 free_unref_page+0xbcf/0xf80 mm/page_alloc.c:2842
 __free_pages+0x6b/0x3b0 mm/page_alloc.c:5351
 __free_slab+0xb5/0x110 mm/slub.c:2758
 free_slab+0x18/0xe0 mm/slub.c:2781
 discard_slab mm/slub.c:2787 [inline]
 __put_partials+0x11b/0x150 mm/slub.c:3256
 put_cpu_partial+0x91/0xc0 mm/slub.c:3331
 __slab_free+0x1cf/0x2a0 mm/slub.c:4584
 do_slab_free mm/slub.c:4666 [inline]
 ___cache_free+0xc9/0xe0 mm/slub.c:4777
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0xb5/0x130 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x14f/0x180 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x28/0x90 mm/kasan/common.c:331
 kasan_slab_alloc include/linux/kasan.h:251 [inline]
 slab_post_alloc_hook mm/slub.c:4202 [inline]
 slab_alloc_node mm/slub.c:4251 [inline]
 kmem_cache_alloc_noprof+0x1bf/0x410 mm/slub.c:4260
 vm_area_dup+0x42/0x570 kernel/fork.c:499
 __split_vma+0x1d5/0xab0 mm/vma.c:384
 split_vma mm/vma.c:468 [inline]
 vma_modify+0x379/0x1670 mm/vma.c:1458
 vma_modify_flags+0x182/0x1c0 mm/vma.c:1484

Memory state around the buggy address:
 ffff888133d39500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888133d39580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888133d39600: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                         ^
 ffff888133d39680: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff888133d39700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/12 19:53 android16-6.12 8509f529f4f8 504cb1bf .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in pick_link
2026/02/12 18:20 android16-6.12 8509f529f4f8 504cb1bf .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in pick_link
* Struck through repros no longer work on HEAD.