From 896665af83060fb673fc12081083f53a10a19dc5 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Date: Fri, 17 Jan 2020 12:00:36 +0100 Subject: [PATCH 2/3] 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: Philippe Mathieu-Daudé Message-id: <20200117120037.12800-3-philmd@redhat.com> Patchwork-id: 93396 O-Subject: [RHEL-7.7.z qemu-kvm + RHEL-7.8 qemu-kvm + RHEL-7.9 qemu-kvm PATCH v2 2/3] slirp: use correct size while emulating IRC commands Bugzilla: 1791560 RH-Acked-by: Stefano Garzarella RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Thomas Huth 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: Philippe Mathieu-Daudé Signed-off-by: Miroslav Rezanina --- 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 70a4c83..321c2a4 100644 --- a/slirp/tcp_subr.c +++ b/slirp/tcp_subr.c @@ -728,7 +728,7 @@ 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); @@ -739,7 +739,7 @@ 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); @@ -750,7 +750,7 @@ 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); -- 1.8.3.1