Re: [syzbot] [net?] WARNING: suspicious RCU usage in xfrm_send_migrate_state

[Aleksandr Nogikh]

#syz dup: WARNING: suspicious RCU usage in xfrm_nlmsg_multicast


On Fri, Jul 31, 2026 at 9:20 AM syzbot
<syzbot+b9e97485773456b16a4a@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    365f9c7a6b81 Merge branches 'for-next/core' and 'for-next/..
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=14863632580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=72c97575381cec47
> dashboard link: https://syzkaller.appspot.com/bug?extid=b9e97485773456b16a4a
> compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12863632580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11b0e49e580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/eafe0adb7386/disk-365f9c7a.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/29422d607579/vmlinux-365f9c7a.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/98ca955a8b54/Image-365f9c7a.gz.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b9e97485773456b16a4a@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> =============================
> 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.0.17/4942:
>  #0: ffff0000d8a19c50 (&net->xfrm.xfrm_cfg_mutex){+.+.}-{4:4}, at: xfrm_netlink_rcv+0x70/0x9c net/xfrm/xfrm_user.c:3928
>
> stack backtrace:
> CPU: 0 UID: 0 PID: 4942 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
> Call trace:
>  show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
>  __dump_stack+0x30/0x40 lib/dump_stack.c:94
>  dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
>  dump_stack+0x1c/0x28 lib/dump_stack.c:129
>  lockdep_rcu_suspicious+0x168/0x26c kernel/locking/lockdep.c:6876
>  xfrm_nlmsg_multicast net/xfrm/xfrm_user.c:1630 [inline]
>  xfrm_send_migrate_state+0x6b0/0x958 net/xfrm/xfrm_user.c:3340
>  xfrm_do_migrate_state+0x1114/0x1728 net/xfrm/xfrm_user.c:3507
>  xfrm_user_rcv_msg+0x4e0/0x950 net/xfrm/xfrm_user.c:3907
>  netlink_rcv_skb+0x238/0x414 net/netlink/af_netlink.c:2556
>  xfrm_netlink_rcv+0x80/0x9c net/xfrm/xfrm_user.c:3929
>  netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
>  netlink_unicast+0x600/0x7f8 net/netlink/af_netlink.c:1345
>  netlink_sendmsg+0x648/0x948 net/netlink/af_netlink.c:1900
>  sock_sendmsg_nosec net/socket.c:775 [inline]
>  __sock_sendmsg+0xc8/0x17c net/socket.c:790
>  ____sys_sendmsg+0x3d0/0x6c8 net/socket.c:2684
>  ___sys_sendmsg+0x198/0x224 net/socket.c:2738
>  __sys_sendmsg+0x158/0x204 net/socket.c:2770
>  __do_sys_sendmsg net/socket.c:2775 [inline]
>  __se_sys_sendmsg net/socket.c:2773 [inline]
>  __arm64_sys_sendmsg+0x80/0x94 net/socket.c:2773
>  __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
>  invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
>  el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
>  do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
>  el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:736
>  el0t_64_sync_handler+0x48/0x148 arch/arm64/kernel/entry-common.c:755
>  el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:594
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx.
> To view this discussion visit https://groups.google.com/d/msgid/syzkaller-bugs/6a6c4cb6.77639fcc.3d4fd0.0021.GAE%40google.com.