From a89949eb46b41533234c4dea0e5a011bc2e583ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@redhat.com>
Date: Mon, 8 Jul 2019 15:50:31 +0100
Subject: [PATCH 4/7] slirp: don't manipulate so_rcv in tcp_emu()
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RH-Author: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: <20190708155031.7778-5-philmd@redhat.com>
Patchwork-id: 89428
O-Subject: [RHEL-8.0.0 qemu-kvm PATCH 4/4] slirp: don't manipulate so_rcv in tcp_emu()
Bugzilla: 1732324
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>

From: Marc-André Lureau <marcandre.lureau@redhat.com>

For some reason, EMU_IDENT is not like other "emulated" protocols and
tries to reconstitute the original buffer, if it came in multiple
packets. Unfortunately, it does so wrongly, as it doesn't respect the
sbuf circular buffer appending rules, nor does it maintain some of the
invariants (rptr is incremented without bounds, etc): this leads to
further memory corruption revealed by ASAN or various malloc
errors. Furthermore, the so_rcv buffer is regularly flushed, so there
is no guarantee that buffer reconstruction will do what is expected.

Instead, do what the function comment says: "XXX Assumes the whole
command came in one packet", and don't touch so_rcv.

Related to: https://bugzilla.redhat.com/show_bug.cgi?id=1664205

Cc: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

(cherry picked from libslirp commit
9da0da837780f825b5db31db6620492f8b7cd5d6)
[ MA - backported with style conflicts, and without qemu commit
a7104eda7dab99d0cdbd3595c211864cba415905 which is unnecessary with
this patch ]
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 slirp/tcp_subr.c | 62 ++++++++++++++++++++++++--------------------------------
 1 file changed, 27 insertions(+), 35 deletions(-)

diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
index e245e0d..0152f72 100644
--- a/slirp/tcp_subr.c
+++ b/slirp/tcp_subr.c
@@ -636,47 +636,39 @@ tcp_emu(struct socket *so, struct mbuf *m)
 			struct socket *tmpso;
 			struct sockaddr_in addr;
 			socklen_t addrlen = sizeof(struct sockaddr_in);
-			struct sbuf *so_rcv = &so->so_rcv;
+			char *eol = g_strstr_len(m->m_data, m->m_len, "\r\n");
 
-			if (m->m_len > so_rcv->sb_datalen
-					- (so_rcv->sb_wptr - so_rcv->sb_data)) {
-			    return 1;
+			if (!eol) {
+				return 1;
 			}
 
-			memcpy(so_rcv->sb_wptr, m->m_data, m->m_len);
-			so_rcv->sb_wptr += m->m_len;
-			so_rcv->sb_rptr += m->m_len;
-			m_inc(m, m->m_len + 1);
-			m->m_data[m->m_len] = 0; /* NULL terminate */
-			if (strchr(m->m_data, '\r') || strchr(m->m_data, '\n')) {
-				if (sscanf(so_rcv->sb_data, "%u%*[ ,]%u", &n1, &n2) == 2) {
-					HTONS(n1);
-					HTONS(n2);
-					/* n2 is the one on our host */
-					for (tmpso = slirp->tcb.so_next;
-					     tmpso != &slirp->tcb;
-					     tmpso = tmpso->so_next) {
-						if (tmpso->so_laddr.s_addr == so->so_laddr.s_addr &&
-						    tmpso->so_lport == n2 &&
-						    tmpso->so_faddr.s_addr == so->so_faddr.s_addr &&
-						    tmpso->so_fport == n1) {
-							if (getsockname(tmpso->s,
-								(struct sockaddr *)&addr, &addrlen) == 0)
-							   n2 = addr.sin_port;
-							break;
-						}
+			*eol = '\0';
+			if (sscanf(m->m_data, "%u%*[ ,]%u", &n1, &n2) == 2) {
+				HTONS(n1);
+				HTONS(n2);
+				/* n2 is the one on our host */
+				for (tmpso = slirp->tcb.so_next; tmpso != &slirp->tcb;
+					 tmpso = tmpso->so_next) {
+					if (tmpso->so_laddr.s_addr == so->so_laddr.s_addr &&
+						tmpso->so_lport == n2 &&
+						tmpso->so_faddr.s_addr == so->so_faddr.s_addr &&
+						tmpso->so_fport == n1) {
+						if (getsockname(tmpso->s, (struct sockaddr *)&addr,
+										&addrlen) == 0)
+							n2 = addr.sin_port;
+						break;
 					}
-					NTOHS(n1);
-					NTOHS(n2);
-					so_rcv->sb_cc = snprintf(so_rcv->sb_data,
-								 so_rcv->sb_datalen,
-								 "%d,%d\r\n", n1, n2);
-					so_rcv->sb_rptr = so_rcv->sb_data;
-					so_rcv->sb_wptr = so_rcv->sb_data + so_rcv->sb_cc;
 				}
+				NTOHS(n1);
+				NTOHS(n2);
+				m_inc(m, snprintf(NULL, 0, "%d,%d\r\n", n1, n2) + 1);
+				m->m_len = snprintf(m->m_data, M_ROOM(m), "%d,%d\r\n", n1, n2);
+				assert(m->m_len < M_ROOM(m));
+			} else {
+				*eol = '\r';
 			}
-			m_free(m);
-			return 0;
+
+			return 1;
 		}
 
         case EMU_FTP: /* ftp */
-- 
1.8.3.1