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From bc779a1a5b3035133024b21e2f339fe4219fb11c Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Mon, 23 May 2016 20:18:34 +0200
Subject: [PATCH] CVE-2016-4429: sunrpc: Do not use alloca in clntudp_call [BZ
#20112]
The call is technically in a loop, and under certain circumstances
(which are quite difficult to reproduce in a test case), alloca
can be invoked repeatedly during a single call to clntudp_call.
As a result, the available stack space can be exhausted (even
though individual alloca sizes are bounded implicitly by what
can fit into a UDP packet, as a side effect of the earlier
successful send operation).
Upstream-Status: Backport
CVE: CVE-2016-4429
Signed-off-by: Armin Kuster <akuster@mvista.com>
---
ChangeLog | 7 +++++++
NEWS | 4 ++++
sunrpc/clnt_udp.c | 10 +++++++++-
3 files changed, 20 insertions(+), 1 deletion(-)
Index: git/ChangeLog
===================================================================
--- git.orig/ChangeLog
+++ git/ChangeLog
@@ -1,3 +1,10 @@
+2016-05-23 Florian Weimer <fweimer@redhat.com>
+
+ CVE-2016-4429
+ [BZ #20112]
+ * sunrpc/clnt_udp.c (clntudp_call): Use malloc/free for the error
+ payload.
+
2016-04-29 Florian Weimer <fweimer@redhat.com>
[BZ #20010]
Index: git/NEWS
===================================================================
--- git.orig/NEWS
+++ git/NEWS
@@ -5,6 +5,11 @@ See the end for copying conditions.
Security related changes:
[Add security related changes here]
+
+* The Sun RPC UDP client could exhaust all available stack space when
+ flooded with crafted ICMP and UDP messages. Reported by Aldy Hernandez'
+ alloca plugin for GCC. (CVE-2016-4429)
+
* Previously, getaddrinfo copied large amounts of address data to the stack,
even after the fix for CVE-2013-4458 has been applied, potentially
resulting in a stack overflow. getaddrinfo now uses a heap allocation
Index: git/sunrpc/clnt_udp.c
===================================================================
--- git.orig/sunrpc/clnt_udp.c
+++ git/sunrpc/clnt_udp.c
@@ -420,9 +420,15 @@ send_again:
struct sock_extended_err *e;
struct sockaddr_in err_addr;
struct iovec iov;
- char *cbuf = (char *) alloca (outlen + 256);
+ char *cbuf = malloc (outlen + 256);
int ret;
+ if (cbuf == NULL)
+ {
+ cu->cu_error.re_errno = errno;
+ return (cu->cu_error.re_status = RPC_CANTRECV);
+ }
+
iov.iov_base = cbuf + 256;
iov.iov_len = outlen;
msg.msg_name = (void *) &err_addr;
@@ -447,10 +453,12 @@ send_again:
cmsg = CMSG_NXTHDR (&msg, cmsg))
if (cmsg->cmsg_level == SOL_IP && cmsg->cmsg_type == IP_RECVERR)
{
+ free (cbuf);
e = (struct sock_extended_err *) CMSG_DATA(cmsg);
cu->cu_error.re_errno = e->ee_errno;
return (cu->cu_error.re_status = RPC_CANTRECV);
}
+ free (cbuf);
}
#endif
do
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