From 0f659af4870f151e25a7d2184b9a383bff58e3ba Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Date: Fri, 17 Jan 2020 12:07:57 +0100 Subject: [PATCH 2/4] slirp: use correct size while emulating IRC commands MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Marc-André Lureau Message-id: <20200117120758.1076549-3-marcandre.lureau@redhat.com> Patchwork-id: 93400 O-Subject: [RHEL-AV-8.1.0 qemu-kvm + RHEL-AV-8.2.0 qemu-kvm PATCH 2/3] slirp: use correct size while emulating IRC commands Bugzilla: 1791568 RH-Acked-by: Philippe Mathieu-Daudé RH-Acked-by: Stefano Garzarella RH-Acked-by: Stefan Hajnoczi From: Prasad J Pandit 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 Signed-off-by: Prasad J Pandit Reviewed-by: Samuel Thibault Message-Id: <20200109094228.79764-2-ppandit@redhat.com> (cherry picked from libslirp commit ce131029d6d4a405cb7d3ac6716d03e58fb4a5d9) Signed-off-by: Marc-André Lureau Signed-off-by: Miroslav Rezanina --- slirp/src/tcp_subr.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/slirp/src/tcp_subr.c b/slirp/src/tcp_subr.c index cbecd64..cedbfb2 100644 --- a/slirp/src/tcp_subr.c +++ b/slirp/src/tcp_subr.c @@ -778,7 +778,8 @@ int 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, "DCC CHAT chat %lu %u%c\n", + 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); } else if (sscanf(bptr, "DCC SEND %256s %u %u %u", buff, &laddr, &lport, @@ -788,8 +789,8 @@ int 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, "DCC SEND %s %lu %u %u%c\n", buff, + 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); } else if (sscanf(bptr, "DCC MOVE %256s %u %u %u", buff, &laddr, &lport, @@ -799,8 +800,8 @@ int 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, "DCC MOVE %s %lu %u %u%c\n", buff, + 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); } -- 1.8.3.1