File 0114-slirp-use-correct-size-while-emulat.patch of Package qemu-linux-user.28156

From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Thu, 9 Jan 2020 15:12:27 +0530
Subject: slirp: use correct size while emulating IRC commands

Git-commit: ce131029d6d4a405cb7d3ac6716d03e58fb4a5d9
References: bsc#1161066, CVE-2020-7039, bsc#1163018, CVE-2020-8608

While emulating IRC DCC commands, tcp_emu() uses 'mbuf' size
'm->m_size' to write DCC commands via snprintf(3). This may
lead to OOB write access, because 'bptr' points somewhere in
the middle of 'mbuf' buffer, not at the start. Use M_FREEROOM(m)
size to avoid OOB access.

Reported-by: Vishnu Dev TJ <vishnudevtj@gmail.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Message-Id: <20200109094228.79764-2-ppandit@redhat.com>
[Since porting from a quite different now libslirp, quite a bit changed]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 slirp/tcp_subr.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
index 624ec008ba7943cbf6eacf7b23d2..1429f27d716db2d8bac454cc3ea3 100644
--- a/slirp/tcp_subr.c
+++ b/slirp/tcp_subr.c
@@ -779,7 +779,7 @@ tcp_emu(struct socket *so, struct mbuf *m)
 				return 1;
 			}
 			m->m_len = bptr - m->m_data; /* Adjust length */
-                        m->m_len += snprintf(bptr, m->m_size,
+                        m->m_len += snprintf(bptr, M_FREEROOM(m),
                                              "DCC CHAT chat %lu %u%c\n",
                                              (unsigned long)ntohl(so->so_faddr.s_addr),
                                              ntohs(so->so_fport), 1);
@@ -790,7 +790,7 @@ tcp_emu(struct socket *so, struct mbuf *m)
 				return 1;
 			}
 			m->m_len = bptr - m->m_data; /* Adjust length */
-                        m->m_len += snprintf(bptr, m->m_size,
+                        m->m_len += snprintf(bptr, M_FREEROOM(m),
                                              "DCC SEND %s %lu %u %u%c\n", buff,
                                              (unsigned long)ntohl(so->so_faddr.s_addr),
                                              ntohs(so->so_fport), n1, 1);
@@ -801,7 +801,7 @@ tcp_emu(struct socket *so, struct mbuf *m)
 				return 1;
 			}
 			m->m_len = bptr - m->m_data; /* Adjust length */
-                        m->m_len += snprintf(bptr, m->m_size,
+                        m->m_len += snprintf(bptr, M_FREEROOM(m),
                                              "DCC MOVE %s %lu %u %u%c\n", buff,
                                              (unsigned long)ntohl(so->so_faddr.s_addr),
                                              ntohs(so->so_fport), n1, 1);