linux-kernel - Re: [syzbot] [net?] KASAN: slab-use-after-free Write in __xfrm_state

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Message-ID: <68aea537.a70a0220.3cafd4.000d.GAE@google.com>
Date: Tue, 26 Aug 2025 23:27:03 -0700
From: syzbot <syzbot+a25ee9d20d31e483ba7b@...kaller.appspotmail.com>
To: hdanton@...a.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] KASAN: slab-use-after-free Write in __xfrm_state_delete

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in xfrm_state_flush

------------[ cut here ]------------
WARNING: CPU: 1 PID: 13 at net/xfrm/xfrm_state.c:801 __xfrm_state_destroy net/xfrm/xfrm_state.c:801 [inline]
WARNING: CPU: 1 PID: 13 at net/xfrm/xfrm_state.c:801 xfrm_state_put include/net/xfrm.h:929 [inline]
WARNING: CPU: 1 PID: 13 at net/xfrm/xfrm_state.c:801 xfrm_state_flush+0x7d9/0x910 net/xfrm/xfrm_state.c:950
Modules linked in:
CPU: 1 UID: 0 PID: 13 Comm: kworker/u8:1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: netns cleanup_net
RIP: 0010:__xfrm_state_destroy net/xfrm/xfrm_state.c:801 [inline]
RIP: 0010:xfrm_state_put include/net/xfrm.h:929 [inline]
RIP: 0010:xfrm_state_flush+0x7d9/0x910 net/xfrm/xfrm_state.c:950
Code: bd 1d 9f f7 90 0f 0b 90 e9 33 fd ff ff e8 af 1d 9f f7 4c 89 e7 be 03 00 00 00 e8 32 6d a7 fa e9 01 fe ff ff e8 98 1d 9f f7 90 <0f> 0b 90 e9 50 fe ff ff e8 8a 1d 9f f7 4c 89 e7 be 03 00 00 00 e8
RSP: 0018:ffffc90000127820 EFLAGS: 00010293
RAX: ffffffff8a208d98 RBX: ffff88807a6fddc0 RCX: ffff88801cec8000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000005
RBP: 0000000000000001 R08: ffff88807a6fde2b R09: 1ffff1100f4dfbc5
R10: dffffc0000000000 R11: ffffed100f4dfbc6 R12: ffff88807a6fde28
R13: ffff88807a6fdef0 R14: dffffc0000000000 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888125d1a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1ca06d5e9c CR3: 0000000074866000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 xfrm6_tunnel_net_exit+0x3c/0x100 net/ipv6/xfrm6_tunnel.c:337
 ops_exit_list net/core/net_namespace.c:198 [inline]
 ops_undo_list+0x49a/0x990 net/core/net_namespace.c:251
 cleanup_net+0x4c5/0x800 net/core/net_namespace.c:682
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3f9/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


Tested on:

commit:         24204116 Merge branch 'ipv6-sr-simplify-and-optimize-h..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13939ef0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=67b99ceb67d33475
dashboard link: https://syzkaller.appspot.com/bug?extid=a25ee9d20d31e483ba7b
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
patch:          https://syzkaller.appspot.com/x/patch.diff?x=150ca462580000