[PATCH net] mptcp: fix locking in mptcp_disconnect()

[PATCH net] mptcp: fix locking in mptcp_disconnect()

[Paolo Abeni]

tcp_disconnect() expects the caller acquires the sock lock,
but mptcp_disconnect() is not doing that. Add the missing
required lock.

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Fixes: 76e2a55d1625 ("mptcp: better msk-level shutdown.")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/mptcp/protocol.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 81faeff8f3bb..f998a077c7dd 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2646,8 +2646,13 @@ static int mptcp_disconnect(struct sock *sk, int flags)
 	struct mptcp_sock *msk = mptcp_sk(sk);
 
 	__mptcp_flush_join_list(msk);
-	mptcp_for_each_subflow(msk, subflow)
-		tcp_disconnect(mptcp_subflow_tcp_sock(subflow), flags);
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		lock_sock(ssk);
+		tcp_disconnect(ssk, flags);
+		release_sock(ssk);
+	}
 	return 0;
 }
 
-- 
2.26.2

Re: [PATCH net] mptcp: fix locking in mptcp_disconnect()

[Eric Dumazet]

On 1/14/21 4:37 PM, Paolo Abeni wrote:
> tcp_disconnect() expects the caller acquires the sock lock,
> but mptcp_disconnect() is not doing that. Add the missing
> required lock.
> 
> Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
> Fixes: 76e2a55d1625 ("mptcp: better msk-level shutdown.")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
>  net/mptcp/protocol.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 81faeff8f3bb..f998a077c7dd 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -2646,8 +2646,13 @@ static int mptcp_disconnect(struct sock *sk, int flags)
>  	struct mptcp_sock *msk = mptcp_sk(sk);
>  
>  	__mptcp_flush_join_list(msk);
> -	mptcp_for_each_subflow(msk, subflow)
> -		tcp_disconnect(mptcp_subflow_tcp_sock(subflow), flags);
> +	mptcp_for_each_subflow(msk, subflow) {
> +		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
> +
> +		lock_sock(ssk);
> +		tcp_disconnect(ssk, flags);
> +		release_sock(ssk);
> +	}

Reviewed-by: Eric Dumazet <edumazet@google.com>

Note that for loops like this one, calling non blocking functions,
you could use lock_sock_fast()

(Probably does not matter in slow path)

Re: [PATCH net] mptcp: fix locking in mptcp_disconnect()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Thu, 14 Jan 2021 16:37:37 +0100 you wrote:
> tcp_disconnect() expects the caller acquires the sock lock,
> but mptcp_disconnect() is not doing that. Add the missing
> required lock.
> 
> Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
> Fixes: 76e2a55d1625 ("mptcp: better msk-level shutdown.")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> 
> [...]

Here is the summary with links:
  - [net] mptcp: fix locking in mptcp_disconnect()
    https://git.kernel.org/netdev/net/c/13a9499e8333

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html