Re: [PATCH bpf-next v1 1/3] bpf, sockmap: avoid using sk_socket after free

[John Fastabend]

On 2025-02-27 11:45:53, Cong Wang wrote:
> On Wed, Feb 26, 2025 at 09:22:40PM +0800, Jiayuan Chen wrote:
> > Use RCU lock to protect sk_socket, preventing concurrent close and release
> > by another thread.
> > 
> > Because TCP/UDP are already within a relatively large critical section:
> > '''
> > ip_local_deliver_finish
> >   rcu_read_lock
> >   ip_protocol_deliver_rcu
> >       tcp_rcv/udp_rcv
> >   rcu_read_unlock
> > '''
> > 
> > Adding rcu_read_{un}lock() at the entrance and exit of sk_data_ready
> > will not increase performance overhead.
> > 
> > Reported-by: syzbot+dd90a702f518e0eac072@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Closes: https://lore.kernel.org/bpf/6734c033.050a0220.2a2fcc.0015.GAE@xxxxxxxxxx/
> > Signed-off-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxx>
> 
> sock_def_readable() already acquires RCU read lock anyway.
> 
> Reviewed-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>

Thanks.

Reviewed-by: John Fastabend <john.fastabend@xxxxxxxxx>