From 0b03959b72036afce151783720d9e54988cf76ef Mon Sep 17 00:00:00 2001 From: Changqing Li Date: Thu, 27 Feb 2020 12:15:04 +0800 Subject: [PATCH] slirp: use correct size while emulating IRC commands 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: default avatarVishnu Dev TJ Signed-off-by: default avatarPrasad J Pandit Reviewed-by: Samuel Thibault's avatarSamuel Thibault Message-Id: <20200109094228.79764-2-ppandit@redhat.com> CVE: CVE-2020-7039 Upstream-Status: Backport [https://gitlab.freedesktop.org/slirp/libslirp/commit/ce131029d6d4a405cb7d3ac6716d03e58fb4a5d9] Signed-off-by: Changqing Li --- 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 e8ed4ef..3a4a8ee 100644 --- a/slirp/src/tcp_subr.c +++ b/slirp/src/tcp_subr.c @@ -777,7 +777,8 @@ 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, @@ -787,8 +788,8 @@ 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, @@ -798,8 +799,8 @@ 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); } -- 2.7.4