Re: [PATCH] xfrm: add missing RCU read lock in xfrm_send_migrate_state()

[Steffen Klassert <steffen.klassert@secunet.com>]

On Fri, Jul 31, 2026 at 10:06:20AM +0000, syzbot wrote:
> From: Aleksandr Nogikh <nogikh@google.com>
> 
> xfrm_nlmsg_multicast() requires the RCU read lock to be held because it
> safely dereferences the net->xfrm.nlsk pointer using rcu_dereference().
> When it is called from xfrm_send_migrate_state(), the RCU read lock is not
> held, which triggers a suspicious RCU usage warning:
> 
> WARNING: suspicious RCU usage
> net/xfrm/xfrm_user.c:1630 suspicious rcu_dereference_check() usage!
> 
> Call Trace:
>  lockdep_rcu_suspicious+0x13f/0x1d0 kernel/locking/lockdep.c:6876
>  xfrm_nlmsg_multicast+0x1d8/0x1f0 net/xfrm/xfrm_user.c:1630
>  xfrm_send_migrate_state+0x870/0xae0 net/xfrm/xfrm_user.c:3340
>  xfrm_do_migrate_state+0x1749/0x1e90 net/xfrm/xfrm_user.c:3507
>  xfrm_user_rcv_msg+0x7a8/0xf30 net/xfrm/xfrm_user.c:3907
> 
> Fix this by wrapping the xfrm_nlmsg_multicast() call in
> xfrm_send_migrate_state() with rcu_read_lock() and rcu_read_unlock().
> 
> Fixes: a9d155ea9b44 ("xfrm: add XFRM_MSG_MIGRATE_STATE for single SA migration")
> Assisted-by: Gemini:gemini-3.5-flash Gemini:gemini-3.1-pro-preview syzbot
> Reported-by: syzbot+c0e99a1aa85a286d7a3b@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=c0e99a1aa85a286d7a3b
> Link: https://syzkaller.appspot.com/ai_job?id=8977f559-3a7e-4bb5-b4d6-1196956260b6
> Signed-off-by: Aleksandr Nogikh <nogikh@google.com>

Applied, thanks a lot!