[PATCH 5.8 16/16] mptcp: free acked data before waiting for more memory

[Greg Kroah-Hartman]

From: Florian Westphal <f...@strlen.de>

[ 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 <f...@strlen.de>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/mptcp/protocol.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- 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;
                        }
                }
        }