From 8f67e76e4148e37f3d8d2bcbdee7417fdedb7669 Mon Sep 17 00:00:00 2001 From: Changqing Li Date: Thu, 27 Feb 2020 12:10:34 +0800 Subject: [PATCH] slirp: use correct size while emulating commands While emulating services in tcp_emu(), it uses 'mbuf' size 'm->m_size' to write commands via snprintf(3). Use M_FREEROOM(m) size to avoid possible OOB access. Signed-off-by: default avatarPrasad J Pandit Signed-off-by: Samuel Thibault's avatarSamuel Thibault Message-Id: <20200109094228.79764-3-ppandit@redhat.com> CVE: CVE-2020-7039 Upstream-Status: Backport [https://gitlab.freedesktop.org/slirp/libslirp/commit/82ebe9c370a0e2970fb5695aa19aa5214a6a1c80] Signed-off-by: Changqing Li --- slirp/src/tcp_subr.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/slirp/src/tcp_subr.c b/slirp/src/tcp_subr.c index 4bea2d4..e8ed4ef 100644 --- a/slirp/src/tcp_subr.c +++ b/slirp/src/tcp_subr.c @@ -696,7 +696,7 @@ int tcp_emu(struct socket *so, struct mbuf *m) n4 = (laddr & 0xff); m->m_len = bptr - m->m_data; /* Adjust length */ - m->m_len += snprintf(bptr, m->m_size - m->m_len, + m->m_len += snprintf(bptr, M_FREEROOM(m), "ORT %d,%d,%d,%d,%d,%d\r\n%s", n1, n2, n3, n4, n5, n6, x == 7 ? buff : ""); return 1; @@ -731,8 +731,7 @@ int tcp_emu(struct socket *so, struct mbuf *m) n4 = (laddr & 0xff); m->m_len = bptr - m->m_data; /* Adjust length */ - m->m_len += - snprintf(bptr, m->m_size - m->m_len, + m->m_len += snprintf(bptr, M_FREEROOM(m), "27 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n%s", n1, n2, n3, n4, n5, n6, x == 7 ? buff : ""); @@ -758,8 +757,8 @@ int tcp_emu(struct socket *so, struct mbuf *m) if (m->m_data[m->m_len - 1] == '\0' && lport != 0 && (so = tcp_listen(slirp, INADDR_ANY, 0, so->so_laddr.s_addr, htons(lport), SS_FACCEPTONCE)) != NULL) - m->m_len = - snprintf(m->m_data, m->m_size, "%d", ntohs(so->so_fport)) + 1; + m->m_len = snprintf(m->m_data, M_ROOM(m), + "%d", ntohs(so->so_fport)) + 1; return 1; case EMU_IRC: -- 2.7.4