linux-kernel - Re: [PATCH] netlink: Fix the netlink socket malfunction due to concurrency

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Date:   Sat, 19 Aug 2023 11:04:48 -0700
From:   Qingjie Xing <xqjcool@...il.com>
To:     edumazet@...gle.com
Cc:     davem@...emloft.net, dhowells@...hat.com, fw@...len.de,
        johannes@...solutions.net, keescook@...omium.org, kuba@...nel.org,
        kuniyu@...zon.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, pabeni@...hat.com, pctammela@...atatu.com,
        xqjcool@...il.com
Subject: Re: [PATCH] netlink: Fix the netlink socket malfunction due to concurrency

This piece of code has been present since the Linux code v2.6.12 was
incorporated into Git management.
I believe this modification could potentially address the concurrent issue
we've been discussing.
In netlink_rcv_wake(), as described in [2], the socket's receive queue is
empty, indicated by sk_rmem_alloc being 0. At this point, concurrent
netlink_attachskb() calls netlink_overrun(). In this critical state, the
sk_rmem_alloc of the socket will not instantly transition from 0 to a
value greater than sk_rcvbuf.