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

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 <redacted>
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

On 1/14/21 4:37 PM, Paolo Abeni wrote:

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)

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 <redacted>
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!
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