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From 9a7810c257711ce02627916d886fc1029f7a8190 Mon Sep 17 00:00:00 2001
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From: jmaloy <jmaloy@redhat.com>
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Date: Thu, 13 Feb 2020 15:50:49 +0000
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Subject: [PATCH 3/7] tcp_emu: fix unsafe snprintf() usages
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: jmaloy <jmaloy@redhat.com>
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Message-id: <20200213155049.3936-3-jmaloy@redhat.com>
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Patchwork-id: 93826
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O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH 2/2] tcp_emu: fix unsafe snprintf() usages
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Bugzilla: 1798994
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RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
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RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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From: Marc-André Lureau <marcandre.lureau@redhat.com>
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Various calls to snprintf() assume that snprintf() returns "only" the
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number of bytes written (excluding terminating NUL).
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https://pubs.opengroup.org/onlinepubs/9699919799/functions/snprintf.html#tag_16_159_04
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"Upon successful completion, the snprintf() function shall return the
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number of bytes that would be written to s had n been sufficiently
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large excluding the terminating null byte."
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Before patch ce131029, if there isn't enough room in "m_data" for the
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"DCC ..." message, we overflow "m_data".
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After the patch, if there isn't enough room for the same, we don't
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overflow "m_data", but we set "m_len" out-of-bounds. The next time an
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access is bounded by "m_len", we'll have a buffer overflow then.
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Use slirp_fmt*() to fix potential OOB memory access.
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Reported-by: Laszlo Ersek <lersek@redhat.com>
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Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
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Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
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Message-Id: <20200127092414.169796-7-marcandre.lureau@redhat.com>
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(cherry picked from libslirp commit 68ccb8021a838066f0951d4b2817eb6b6f10a843)
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Signed-off-by: Jon Maloy <jmaloy@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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slirp/src/tcp_subr.c | 44 +++++++++++++++++++++-----------------------
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1 file changed, 21 insertions(+), 23 deletions(-)
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diff --git a/slirp/src/tcp_subr.c b/slirp/src/tcp_subr.c
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index 954d1a6..26d4ead 100644
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--- a/slirp/src/tcp_subr.c
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+++ b/slirp/src/tcp_subr.c
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@@ -655,8 +655,7 @@ int tcp_emu(struct socket *so, struct mbuf *m)
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NTOHS(n1);
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NTOHS(n2);
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m_inc(m, snprintf(NULL, 0, "%d,%d\r\n", n1, n2) + 1);
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- m->m_len = snprintf(m->m_data, M_ROOM(m), "%d,%d\r\n", n1, n2);
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- assert(m->m_len < M_ROOM(m));
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+ m->m_len = slirp_fmt(m->m_data, M_ROOM(m), "%d,%d\r\n", n1, n2);
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} else {
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*eol = '\r';
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}
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@@ -696,9 +695,9 @@ int tcp_emu(struct socket *so, struct mbuf *m)
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n4 = (laddr & 0xff);
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m->m_len = bptr - m->m_data; /* Adjust length */
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- m->m_len += snprintf(bptr, M_FREEROOM(m),
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- "ORT %d,%d,%d,%d,%d,%d\r\n%s", n1, n2, n3, n4,
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- n5, n6, x == 7 ? buff : "");
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+ m->m_len += slirp_fmt(bptr, M_FREEROOM(m),
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+ "ORT %d,%d,%d,%d,%d,%d\r\n%s",
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+ n1, n2, n3, n4, n5, n6, x == 7 ? buff : "");
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return 1;
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} else if ((bptr = (char *)strstr(m->m_data, "27 Entering")) != NULL) {
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/*
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@@ -731,10 +730,9 @@ int tcp_emu(struct socket *so, struct mbuf *m)
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n4 = (laddr & 0xff);
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m->m_len = bptr - m->m_data; /* Adjust length */
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- m->m_len += snprintf(bptr, M_FREEROOM(m),
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- "27 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n%s",
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- n1, n2, n3, n4, n5, n6, x == 7 ? buff : "");
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-
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+ m->m_len += slirp_fmt(bptr, M_FREEROOM(m),
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+ "27 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n%s",
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+ n1, n2, n3, n4, n5, n6, x == 7 ? buff : "");
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return 1;
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}
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@@ -757,8 +755,8 @@ int tcp_emu(struct socket *so, struct mbuf *m)
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if (m->m_data[m->m_len - 1] == '\0' && lport != 0 &&
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(so = tcp_listen(slirp, INADDR_ANY, 0, so->so_laddr.s_addr,
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htons(lport), SS_FACCEPTONCE)) != NULL)
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- m->m_len = snprintf(m->m_data, M_ROOM(m),
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- "%d", ntohs(so->so_fport)) + 1;
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+ m->m_len = slirp_fmt0(m->m_data, M_ROOM(m),
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+ "%d", ntohs(so->so_fport));
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return 1;
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case EMU_IRC:
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@@ -777,10 +775,10 @@ int tcp_emu(struct socket *so, struct mbuf *m)
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return 1;
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}
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m->m_len = bptr - m->m_data; /* Adjust length */
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- m->m_len += snprintf(bptr, M_FREEROOM(m),
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- "DCC CHAT chat %lu %u%c\n",
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- (unsigned long)ntohl(so->so_faddr.s_addr),
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- ntohs(so->so_fport), 1);
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+ m->m_len += slirp_fmt(bptr, M_FREEROOM(m),
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+ "DCC CHAT chat %lu %u%c\n",
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+ (unsigned long)ntohl(so->so_faddr.s_addr),
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+ ntohs(so->so_fport), 1);
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} else if (sscanf(bptr, "DCC SEND %256s %u %u %u", buff, &laddr, &lport,
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&n1) == 4) {
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if ((so = tcp_listen(slirp, INADDR_ANY, 0, htonl(laddr),
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@@ -788,10 +786,10 @@ int tcp_emu(struct socket *so, struct mbuf *m)
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return 1;
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}
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m->m_len = bptr - m->m_data; /* Adjust length */
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- m->m_len += snprintf(bptr, M_FREEROOM(m),
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- "DCC SEND %s %lu %u %u%c\n", buff,
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- (unsigned long)ntohl(so->so_faddr.s_addr),
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- ntohs(so->so_fport), n1, 1);
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+ m->m_len += slirp_fmt(bptr, M_FREEROOM(m),
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+ "DCC SEND %s %lu %u %u%c\n", buff,
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+ (unsigned long)ntohl(so->so_faddr.s_addr),
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+ ntohs(so->so_fport), n1, 1);
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} else if (sscanf(bptr, "DCC MOVE %256s %u %u %u", buff, &laddr, &lport,
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&n1) == 4) {
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if ((so = tcp_listen(slirp, INADDR_ANY, 0, htonl(laddr),
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@@ -799,10 +797,10 @@ int tcp_emu(struct socket *so, struct mbuf *m)
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return 1;
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}
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m->m_len = bptr - m->m_data; /* Adjust length */
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- m->m_len += snprintf(bptr, M_FREEROOM(m),
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- "DCC MOVE %s %lu %u %u%c\n", buff,
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- (unsigned long)ntohl(so->so_faddr.s_addr),
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- ntohs(so->so_fport), n1, 1);
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+ m->m_len += slirp_fmt(bptr, M_FREEROOM(m),
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+ "DCC MOVE %s %lu %u %u%c\n", buff,
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+ (unsigned long)ntohl(so->so_faddr.s_addr),
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+ ntohs(so->so_fport), n1, 1);
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}
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return 1;
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--
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1.8.3.1
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