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qemu/tcp_emu-fix-unsafe-snprintf-usages.patch
Bruce Rogers baeb560873 Accepting request 785936 from home:bfrogers:branches:Virtualization 
- Fix potential OOB accesses in slirp (CVE-2020-8608 bsc#1163018
  bsc#1161066 CVE-2020-7039)
  slirp-use-correct-size-while-emulating-c.patch
  slirp-use-correct-size-while-emulating-I.patch
  tcp_emu-Fix-oob-access.patch
  tcp_emu-fix-unsafe-snprintf-usages.patch
  util-add-slirp_fmt-helpers.patch
- Replace this patch with upstream version
  target-arm-monitor-query-cpu-model-expan.patch

OBS-URL: https://build.opensuse.org/request/show/785936
OBS-URL: https://build.opensuse.org/package/show/Virtualization/qemu?expand=0&rev=536
2020-03-17 13:47:06 +00:00

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From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
Date: Mon, 27 Jan 2020 10:24:14 +0100
Subject: tcp_emu: fix unsafe snprintf() usages
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Git-commit: 68ccb8021a838066f0951d4b2817eb6b6f10a843
References: bsc#1163018, CVE-2020-8608
Various calls to snprintf() assume that snprintf() returns "only" the
number of bytes written (excluding terminating NUL).
https://pubs.opengroup.org/onlinepubs/9699919799/functions/snprintf.html#tag_16_159_04
"Upon successful completion, the snprintf() function shall return the
number of bytes that would be written to s had n been sufficiently
large excluding the terminating null byte."
Before patch ce131029, if there isn't enough room in "m_data" for the
"DCC ..." message, we overflow "m_data".
After the patch, if there isn't enough room for the same, we don't
overflow "m_data", but we set "m_len" out-of-bounds. The next time an
access is bounded by "m_len", we'll have a buffer overflow then.
Use slirp_fmt*() to fix potential OOB memory access.
Reported-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Message-Id: <20200127092414.169796-7-marcandre.lureau@redhat.com>
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
src/tcp_subr.c | 44 +++++++++++++++++++++-----------------------
1 file changed, 21 insertions(+), 23 deletions(-)
diff --git a/slirp/src/tcp_subr.c b/slirp/src/tcp_subr.c
index 954d1a6f5e6292b585638a8c0558..26d4ead543a5357577817b39a3d6 100644
--- a/slirp/src/tcp_subr.c
+++ b/slirp/src/tcp_subr.c
@@ -655,8 +655,7 @@ int tcp_emu(struct socket *so, struct mbuf *m)
NTOHS(n1);
NTOHS(n2);
m_inc(m, snprintf(NULL, 0, "%d,%d\r\n", n1, n2) + 1);
- m->m_len = snprintf(m->m_data, M_ROOM(m), "%d,%d\r\n", n1, n2);
- assert(m->m_len < M_ROOM(m));
+ m->m_len = slirp_fmt(m->m_data, M_ROOM(m), "%d,%d\r\n", n1, n2);
} else {
*eol = '\r';
}
@@ -696,9 +695,9 @@ 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_FREEROOM(m),
- "ORT %d,%d,%d,%d,%d,%d\r\n%s", n1, n2, n3, n4,
- n5, n6, x == 7 ? buff : "");
+ m->m_len += slirp_fmt(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;
} else if ((bptr = (char *)strstr(m->m_data, "27 Entering")) != NULL) {
/*
@@ -731,10 +730,9 @@ 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_FREEROOM(m),
- "27 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n%s",
- n1, n2, n3, n4, n5, n6, x == 7 ? buff : "");
-
+ m->m_len += slirp_fmt(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 : "");
return 1;
}
@@ -757,8 +755,8 @@ 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_ROOM(m),
- "%d", ntohs(so->so_fport)) + 1;
+ m->m_len = slirp_fmt0(m->m_data, M_ROOM(m),
+ "%d", ntohs(so->so_fport));
return 1;
case EMU_IRC:
@@ -777,10 +775,10 @@ 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_FREEROOM(m),
- "DCC CHAT chat %lu %u%c\n",
- (unsigned long)ntohl(so->so_faddr.s_addr),
- ntohs(so->so_fport), 1);
+ m->m_len += slirp_fmt(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,
&n1) == 4) {
if ((so = tcp_listen(slirp, INADDR_ANY, 0, htonl(laddr),
@@ -788,10 +786,10 @@ 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_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);
+ m->m_len += slirp_fmt(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,
&n1) == 4) {
if ((so = tcp_listen(slirp, INADDR_ANY, 0, htonl(laddr),
@@ -799,10 +797,10 @@ 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_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);
+ m->m_len += slirp_fmt(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);
}
return 1;
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