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mptcp: sendmsg: reset iter on error

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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: 72511aab95 ("mptcp: avoid blocking in tcp_sendpages")
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal 2020-08-14 15:56:34 +02:00 committed by David S. Miller
parent 068885434c
commit 3575938313
1 changed files with 6 additions and 2 deletions
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8
net/mptcp/protocol.c
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@ -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) {