[syzbot] [net?] WARNING: suspicious RCU usage in xfrm_do_migrate_state

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4235cb24ec1e Merge tag 'vfs-7.2-rc5.fixes' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1293a7b1580000
kernel config: https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=d3bc2f2eb498a0175940
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=10a4c49e580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1475bfde580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bfb2ad7db60c/disk-4235cb24.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/dfd0a5b6c4bb/vmlinux-4235cb24.xz
kernel image: https://storage.googleapis.com/syzbot-assets/44b46af35859/bzImage-4235cb24.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d3bc2f...@syzkaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
net/xfrm/xfrm_user.c:1630 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz.0.17/5833:
#0: ffff888032dcc390 (&net->xfrm.xfrm_cfg_mutex){+.+.}-{4:4}, at: xfrm_netlink_rcv+0x62/0x90 net/xfrm/xfrm_user.c:3928

stack backtrace:
CPU: 1 UID: 0 PID: 5833 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
lockdep_rcu_suspicious.cold+0x4f/0xb1 kernel/locking/lockdep.c:6876
xfrm_nlmsg_multicast net/xfrm/xfrm_user.c:1630 [inline]
xfrm_send_migrate_state net/xfrm/xfrm_user.c:3340 [inline]
xfrm_do_migrate_state+0x2463/0x2f10 net/xfrm/xfrm_user.c:3507
xfrm_user_rcv_msg+0x483/0xd80 net/xfrm/xfrm_user.c:3907
netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2556
xfrm_netlink_rcv+0x71/0x90 net/xfrm/xfrm_user.c:3929
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1345
netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1900
sock_sendmsg_nosec net/socket.c:775 [inline]
__sock_sendmsg net/socket.c:790 [inline]
____sys_sendmsg+0xa4d/0xbe0 net/socket.c:2684
___sys_sendmsg+0x190/0x1e0 net/socket.c:2738
__sys_sendmsg+0x160/0x210 net/socket.c:2770
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: 0033:0x7f9a1659de99
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:00007ffe88741d08 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f9a16825fa0 RCX: 00007f9a1659de99
RDX: 0000000000000000 RSI: 0000200000000500 RDI: 0000000000000003
RBP: 00007f9a16633eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9a16825fac R14: 00007f9a16825fa0 R15: 00007f9a16825fa0
</TASK>


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