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

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Message-ID: <68aea933.a70a0220.3cafd4.000e.GAE@google.com>
Date: Tue, 26 Aug 2025 23:44:03 -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: 0 PID: 49 at net/xfrm/xfrm_state.c:801 __xfrm_state_destroy net/xfrm/xfrm_state.c:801 [inline]
WARNING: CPU: 0 PID: 49 at net/xfrm/xfrm_state.c:801 xfrm_state_put include/net/xfrm.h:929 [inline]
WARNING: CPU: 0 PID: 49 at net/xfrm/xfrm_state.c:801 xfrm_state_flush+0x627/0x740 net/xfrm/xfrm_state.c:957
Modules linked in:
CPU: 0 UID: 0 PID: 49 Comm: kworker/u8:3 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+0x627/0x740 net/xfrm/xfrm_state.c:957
Code: 3f 8b 02 f8 48 8b 2b 48 85 ed 0f 84 dd 00 00 00 48 83 c5 f8 0f 84 d3 00 00 00 e8 54 1f 9f f7 e9 b3 fc ff ff e8 4a 1f 9f f7 90 <0f> 0b 90 e9 68 fe ff ff e8 3c 1f 9f f7 48 8b 7c 24 20 be 03 00 00
RSP: 0018:ffffc90000b97820 EFLAGS: 00010293
RAX: ffffffff8a208be6 RBX: 0000000000000001 RCX: ffff888022abbc00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000005
RBP: ffff888029974440 R08: ffff8880299744ab R09: 1ffff1100532e895
R10: dffffc0000000000 R11: ffffed100532e896 R12: 0000000000000001
R13: 0000000000000000 R14: 0000000000000000 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888125c1a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f50d6d1d440 CR3: 000000004dc26000 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=13f39ef0580000
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=1519dc42580000