[PATCH net-next] mptcp: avoid potential infinite loop in mptcp_recvmsg()

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

If a packet is ready in receive queue, and application isssues
a recvmsg()/recvfrom()/recvmmsg() request asking for zero bytes,
we hang in mptcp_recvmsg().

Fixes: ea4ca586b16f ("mptcp: refine MPTCP-level ack scheduling")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Paolo Abeni <pab...@redhat.com>
---
 net/mptcp/protocol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 
221f7cdd416bdb681968bf1b3ff2ed1b03cea3ce..57213ff60f784fae14c2a96f391ccdec6249c168
 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1921,7 +1921,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr 
*msg, size_t len,
        len = min_t(size_t, len, INT_MAX);
        target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
 
-       for (;;) {
+       while (copied < len) {
                int bytes_read, old_space;
 
                bytes_read = __mptcp_recvmsg_mskq(msk, msg, len - copied);
-- 
2.29.2.454.gaff20da3a2-goog