From: Florian Westphal <fw@strlen.de>
Date: Tue, 25 Aug 2020 23:31:05 +0000 (+0200)
Subject: mptcp: free acked data before waiting for more memory
X-Git-Tag: v5.8.9~1
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=cdba995d2f19932db89a91cf0d9a99d6e7d4659e;p=thirdparty%2Fkernel%2Fstable.git

mptcp: free acked data before waiting for more memory

[ Upstream commit 1cec170d458b1d18f6f1654ca84c0804a701c5ef ]

After subflow lock is dropped, more wmem might have been made available.

This fixes a deadlock in mptcp_connect.sh 'mmap' mode: wmem is exhausted.
But as the mptcp socket holds on to already-acked data (for retransmit)
no wakeup will occur.

Using 'goto restart' calls mptcp_clean_una(sk) which will free pages
that have been acked completely in the mean time.

Fixes: fb529e62d3f3 ("mptcp: break and restart in case mptcp sndbuf is full")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index c0abe738e7d31..939e445d5188c 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -772,7 +772,6 @@ fallback:
 restart:
 	mptcp_clean_una(sk);
 
-wait_for_sndbuf:
 	__mptcp_flush_join_list(msk);
 	ssk = mptcp_subflow_get_send(msk);
 	while (!sk_stream_memory_free(sk) ||
@@ -873,7 +872,7 @@ wait_for_sndbuf:
 				 */
 				mptcp_set_timeout(sk, ssk);
 				release_sock(ssk);
-				goto wait_for_sndbuf;
+				goto restart;
 			}
 		}
 	}