From 35759383133f64d90eba120a0d3efe8f71241650 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 14 Aug 2020 15:56:34 +0200 Subject: mptcp: sendmsg: reset iter on error Once we've copied data from the iterator we need to revert in case we end up not sending any data. This bug doesn't trigger with normal 'poll' based tests, because we only feed a small chunk of data to kernel after poll indicated POLLOUT. With blocking IO and large writes this triggers. Receiver ends up with less data than it should get. Fixes: 72511aab95c94d ("mptcp: avoid blocking in tcp_sendpages") Signed-off-by: Florian Westphal Reviewed-by: Mat Martineau Signed-off-by: David S. Miller --- net/mptcp/protocol.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'net') diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 8c1d1a595701..c84b4051c2a4 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -725,8 +725,10 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk, if (!psize) return -EINVAL; - if (!sk_wmem_schedule(sk, psize + dfrag->overhead)) + if (!sk_wmem_schedule(sk, psize + dfrag->overhead)) { + iov_iter_revert(&msg->msg_iter, psize); return -ENOMEM; + } } else { offset = dfrag->offset; psize = min_t(size_t, dfrag->data_len, avail_size); @@ -737,8 +739,10 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk, */ ret = do_tcp_sendpages(ssk, page, offset, psize, msg->msg_flags | MSG_SENDPAGE_NOTLAST | MSG_DONTWAIT); - if (ret <= 0) + if (ret <= 0) { + iov_iter_revert(&msg->msg_iter, psize); return ret; + } frag_truesize += ret; if (!retransmission) { -- cgit v1.2.3