[v6.6] KASAN: slab-use-after-free Read in __xfrm_state_lookup

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syzbot

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Aug 28, 2025, 4:30:33 PM8/28/25
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Hello,

syzbot found the following issue on:

HEAD commit: cc1a1c5b404a Linux 6.6.103
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12dd8262580000
kernel config: https://syzkaller.appspot.com/x/.config?x=412020841cf033b0
dashboard link: https://syzkaller.appspot.com/bug?extid=d2c716154e2b0b6081fd
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/46c06862a545/disk-cc1a1c5b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/38ddabb6fc8b/vmlinux-cc1a1c5b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b130b7d031b5/bzImage-cc1a1c5b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d2c716...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in __xfrm_state_lookup+0x6b2/0x8d0 net/xfrm/xfrm_state.c:1084
Read of size 2 at addr ffff88805eee8122 by task syz.0.3736/14218

CPU: 0 PID: 14218 Comm: syz.0.3736 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xac/0x220 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
__xfrm_state_lookup+0x6b2/0x8d0 net/xfrm/xfrm_state.c:1084
__xfrm_state_locate net/xfrm/xfrm_state.c:1132 [inline]
xfrm_state_add+0x25e/0xe20 net/xfrm/xfrm_state.c:1665
xfrm_add_sa+0x26f7/0x30a0 net/xfrm/xfrm_user.c:805
xfrm_user_rcv_msg+0x596/0x870 net/xfrm/xfrm_user.c:3169
netlink_rcv_skb+0x216/0x480 net/netlink/af_netlink.c:2545
xfrm_netlink_rcv+0x79/0x90 net/xfrm/xfrm_user.c:3191
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x751/0x8d0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x8c1/0xbe0 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x5bf/0x950 net/socket.c:2595
___sys_sendmsg+0x220/0x290 net/socket.c:2649
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2687 [inline]
__se_sys_sendmsg+0x1a5/0x270 net/socket.c:2685
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8eb798ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8eb8752038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f8eb7bb5fa0 RCX: 00007f8eb798ebe9
RDX: 0000000000000000 RSI: 0000200000000180 RDI: 0000000000000003
RBP: 00007f8eb7a11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8eb7bb6038 R14: 00007f8eb7bb5fa0 R15: 00007fff86aebb28
</TASK>

Allocated by task 6038:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
slab_alloc_node mm/slub.c:3485 [inline]
slab_alloc mm/slub.c:3493 [inline]
__kmem_cache_alloc_lru mm/slub.c:3500 [inline]
kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3509
kmem_cache_zalloc include/linux/slab.h:711 [inline]
xfrm_state_alloc+0x22/0x2a0 net/xfrm/xfrm_state.c:661
__find_acq_core+0x7d8/0x19d0 net/xfrm/xfrm_state.c:1598
xfrm_find_acq+0x6a/0x90 net/xfrm/xfrm_state.c:2070
xfrm_alloc_userspi+0x57a/0xa90 net/xfrm/xfrm_user.c:1613
xfrm_user_rcv_msg+0x596/0x870 net/xfrm/xfrm_user.c:3169
netlink_rcv_skb+0x216/0x480 net/netlink/af_netlink.c:2545
xfrm_netlink_rcv+0x79/0x90 net/xfrm/xfrm_user.c:3191
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x751/0x8d0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x8c1/0xbe0 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x5bf/0x950 net/socket.c:2595
___sys_sendmsg+0x220/0x290 net/socket.c:2649
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2687 [inline]
__se_sys_sendmsg+0x1a5/0x270 net/socket.c:2685
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88805eee8000
which belongs to the cache xfrm_state of size 848
The buggy address is located 290 bytes inside of
freed 848-byte region [ffff88805eee8000, ffff88805eee8350)

The buggy address belongs to the physical page:
page:ffffea00017bba00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88805eee9000 pfn:0x5eee8
head:ffffea00017bba00 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff88801b2ba640 dead000000000122 0000000000000000
raw: ffff88805eee9000 0000000080100009 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x152820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL), pid 6038, tgid 6037 (syz.0.85), ts 82736568797, free_ts 82696642916
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
alloc_slab_page+0x5d/0x170 mm/slub.c:1876
allocate_slab mm/slub.c:2023 [inline]
new_slab+0x87/0x2e0 mm/slub.c:2076
___slab_alloc+0xc6d/0x12f0 mm/slub.c:3230
__slab_alloc mm/slub.c:3329 [inline]
__slab_alloc_node mm/slub.c:3382 [inline]
slab_alloc_node mm/slub.c:3475 [inline]
slab_alloc mm/slub.c:3493 [inline]
__kmem_cache_alloc_lru mm/slub.c:3500 [inline]
kmem_cache_alloc+0x1b7/0x2e0 mm/slub.c:3509
kmem_cache_zalloc include/linux/slab.h:711 [inline]
xfrm_state_alloc+0x22/0x2a0 net/xfrm/xfrm_state.c:661
__find_acq_core+0x7d8/0x19d0 net/xfrm/xfrm_state.c:1598
xfrm_find_acq+0x6a/0x90 net/xfrm/xfrm_state.c:2070
xfrm_alloc_userspi+0x57a/0xa90 net/xfrm/xfrm_user.c:1613
xfrm_user_rcv_msg+0x596/0x870 net/xfrm/xfrm_user.c:3169
netlink_rcv_skb+0x216/0x480 net/netlink/af_netlink.c:2545
xfrm_netlink_rcv+0x79/0x90 net/xfrm/xfrm_user.c:3191
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x751/0x8d0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x8c1/0xbe0 net/netlink/af_netlink.c:1894
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
__slab_free+0x35e/0x410 mm/slub.c:3722
qlink_free mm/kasan/quarantine.c:166 [inline]
qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:305
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
slab_alloc_node mm/slub.c:3485 [inline]
slab_alloc mm/slub.c:3493 [inline]
__kmem_cache_alloc_lru mm/slub.c:3500 [inline]
kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3509
getname_flags+0xbb/0x500 fs/namei.c:140
vfs_fstatat+0x111/0x1b0 fs/stat.c:298
__do_sys_newfstatat fs/stat.c:463 [inline]
__se_sys_newfstatat fs/stat.c:457 [inline]
__x64_sys_newfstatat+0x117/0x190 fs/stat.c:457
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
ffff88805eee8000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805eee8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88805eee8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88805eee8180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805eee8200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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syzbot

unread,
Dec 10, 2025, 7:06:15 AM12/10/25
to syzkaller...@googlegroups.com
Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.
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