linux-kernel - Re: [PATCH bpf-next v1 1/3] bpf, sockmap: avoid using sk

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Message-ID: <84f25c32-1aa6-42d6-a5b1-efce822bfcd6@linux.dev>
Date: Thu, 27 Feb 2025 15:04:26 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Jiayuan Chen <jiayuan.chen@...ux.dev>
Cc: cong.wang@...edance.com, john.fastabend@...il.com, jakub@...udflare.com,
 davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
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 sgarzare@...hat.com, netdev@...r.kernel.org, bpf@...r.kernel.org,
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Subject: Re: [PATCH bpf-next v1 1/3] bpf, sockmap: avoid using sk_socket after
 free

On 2/26/25 5:22 AM, 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.

Can it use a Fixes tag?