From: syzbot <syzbot+0962e3a1af6d5e26a52c@syzkaller.appspotmail.com>
To: jmorris@namei.org, linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org, paul@paul-moore.com,
serge@hallyn.com, syzkaller-bugs@googlegroups.com
Subject: [syzbot] [lsm?] KASAN: slab-use-after-free Read in security_inode_follow_link
Date: Fri, 29 May 2026 13:01:28 -0700 [thread overview]
Message-ID: <6a19f098.abb04025.19af7b.0004.GAE@google.com> (raw)
Hello,
syzbot found the following issue on:
HEAD commit: eb3f4b7426cf Merge tag 'nfsd-7.1-2' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17dae52e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8118209836970b54
dashboard link: https://syzkaller.appspot.com/bug?extid=0962e3a1af6d5e26a52c
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14427ed2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=109e452e580000
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-eb3f4b74.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1406171f5cf6/vmlinux-eb3f4b74.xz
kernel image: https://storage.googleapis.com/syzbot-assets/19b8bb9b727a/bzImage-eb3f4b74.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0962e3a1af6d5e26a52c@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: slab-use-after-free in security_inode_follow_link+0x277/0x280 security/security.c:1819
Read of size 4 at addr ffff8880393e0004 by task syz.0.594/8610
CPU: 3 UID: 0 PID: 8610 Comm: syz.0.594 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x13d/0x4b0 mm/kasan/report.c:482
kasan_report+0xdf/0x1d0 mm/kasan/report.c:595
security_inode_follow_link+0x277/0x280 security/security.c:1819
pick_link+0x433/0x13c0 fs/namei.c:2049
step_into_slowpath+0x9ba/0xf90 fs/namei.c:2123
step_into fs/namei.c:2148 [inline]
walk_component fs/namei.c:2284 [inline]
link_path_walk+0xf28/0x1cc0 fs/namei.c:2652
path_parentat fs/namei.c:2856 [inline]
__filename_parentat+0x213/0x740 fs/namei.c:2880
filename_parentat fs/namei.c:2898 [inline]
filename_unlinkat+0xf7/0x730 fs/namei.c:5537
__do_sys_unlinkat fs/namei.c:5597 [inline]
__se_sys_unlinkat fs/namei.c:5589 [inline]
__x64_sys_unlinkat+0xc0/0x130 fs/namei.c:5589
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f60b0f9ce59
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:00007f60b1dc9028 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 00007f60b1215fa0 RCX: 00007f60b0f9ce59
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000000000000006
RBP: 00007f60b1032d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f60b1216038 R14: 00007f60b1215fa0 R15: 00007ffddfc81a28
</TASK>
Allocated by task 8610:
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
unpoison_slab_object mm/kasan/common.c:340 [inline]
__kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:366
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4570 [inline]
slab_alloc_node mm/slub.c:4899 [inline]
kmem_cache_alloc_lru_noprof+0x246/0x6e0 mm/slub.c:4918
alloc_inode+0x183/0x250 fs/inode.c:347
new_inode+0x22/0x1c0 fs/inode.c:1179
bpf_get_inode kernel/bpf/inode.c:117 [inline]
bpf_get_inode kernel/bpf/inode.c:102 [inline]
bpf_symlink+0x69/0x240 kernel/bpf/inode.c:391
vfs_symlink fs/namei.c:5643 [inline]
vfs_symlink+0x178/0x4d0 fs/namei.c:5622
filename_symlinkat+0x2a6/0x560 fs/namei.c:5668
__do_sys_symlinkat fs/namei.c:5688 [inline]
__se_sys_symlinkat fs/namei.c:5683 [inline]
__x64_sys_symlinkat+0x9c/0xe0 fs/namei.c:5683
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 8611:
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2689 [inline]
slab_free mm/slub.c:6251 [inline]
kmem_cache_free+0x127/0x6c0 mm/slub.c:6378
destroy_inode+0xcb/0x1c0 fs/inode.c:394
evict+0x599/0xad0 fs/inode.c:865
iput_final fs/inode.c:1960 [inline]
iput.part.0+0x605/0xf50 fs/inode.c:2009
iput+0x35/0x40 fs/inode.c:1975
filename_unlinkat+0x466/0x730 fs/namei.c:5572
__do_sys_unlinkat fs/namei.c:5597 [inline]
__se_sys_unlinkat fs/namei.c:5589 [inline]
__x64_sys_unlinkat+0xc0/0x130 fs/namei.c:5589
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff8880393e0000
which belongs to the cache inode_cache of size 1088
The buggy address is located 4 bytes inside of
freed 1088-byte region [ffff8880393e0000, ffff8880393e0440)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x393e0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88803ce9f201
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff888100090000 dead000000000100 dead000000000122
raw: 0000000000000000 00000008001a001a 00000000f5000000 ffff88803ce9f201
head: 00fff00000000040 ffff888100090000 dead000000000100 dead000000000122
head: 0000000000000000 00000008001a001a 00000000f5000000 ffff88803ce9f201
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Reclaimable, gfp_mask 0xd20d0(__GFP_RECLAIMABLE|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5753, tgid 5753 (syz-execprog), ts 103858448509, free_ts 0
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1853
prep_new_page mm/page_alloc.c:1861 [inline]
get_page_from_freelist+0x11a6/0x3410 mm/page_alloc.c:3941
__alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5221
alloc_slab_page mm/slub.c:3278 [inline]
allocate_slab mm/slub.c:3467 [inline]
new_slab+0xa6/0x6c0 mm/slub.c:3525
refill_objects+0x277/0x420 mm/slub.c:7272
refill_sheaf mm/slub.c:2816 [inline]
__pcs_replace_empty_main+0x375/0x650 mm/slub.c:4652
alloc_from_pcs mm/slub.c:4750 [inline]
slab_alloc_node mm/slub.c:4884 [inline]
kmem_cache_alloc_lru_noprof+0x485/0x6e0 mm/slub.c:4918
alloc_inode+0x183/0x250 fs/inode.c:347
iget_locked+0x1d9/0x6d0 fs/inode.c:1474
kernfs_get_inode+0x46/0x470 fs/kernfs/inode.c:252
kernfs_iop_lookup+0x1a7/0x2d0 fs/kernfs/dir.c:1274
lookup_open.isra.0+0x631/0x11b0 fs/namei.c:4484
open_last_lookups fs/namei.c:4611 [inline]
path_openat+0xa98/0x31a0 fs/namei.c:4855
do_file_open+0x20e/0x430 fs/namei.c:4887
do_sys_openat2+0x10d/0x1e0 fs/open.c:1364
do_sys_open fs/open.c:1370 [inline]
__do_sys_openat fs/open.c:1386 [inline]
__se_sys_openat fs/open.c:1381 [inline]
__x64_sys_openat+0x12d/0x210 fs/open.c:1381
page_owner free stack trace missing
Memory state around the buggy address:
ffff8880393dff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880393dff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880393e0000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880393e0080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880393e0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
This report is generated by a bot. It may contain errors.
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reply other threads:[~2026-05-29 20:01 UTC|newest]
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