[PATCH 1/5] udp: SECURITY: Pass correct size argument to recvfrom

[Ian Jackson]

Otherwise we risk overflowing the buffer.  This is a critical security
problem.

Signed-off-by: Ian Jackson <ijackson at chiark.greenend.org.uk>
---
 udp.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/udp.c b/udp.c
index 97b92a6..fa42ba4 100644
--- a/udp.c
+++ b/udp.c
@@ -104,8 +104,9 @@ static void udp_afterpoll(void *state, struct pollfd *fds, int nfds)
 	    BUF_ASSERT_FREE(st->rbuf);
 	    BUF_ALLOC(st->rbuf,"udp_afterpoll");
 	    buffer_init(st->rbuf,calculate_max_start_pad());
-	    rv=recvfrom(st->fd, st->rbuf->start, st->rbuf->len, 0,
-			(struct sockaddr *)&from, &fromlen);
+	    rv=recvfrom(st->fd, st->rbuf->start,
+			(st->rbuf->base + st->rbuf->len) - st->rbuf->start,
+			0, (struct sockaddr *)&from, &fromlen);
 	    if (rv>0) {
 		st->rbuf->size=rv;
 		if (st->use_proxy) {
-- 
1.7.10.4