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[PATCH] CVE-2016-4429: sunrpc: Do not use alloca in clntudp_call [BZ #20112]
- From: fweimer at redhat dot com (Florian Weimer)
- To: libc-alpha at sourceware dot org
- Date: Thu, 19 May 2016 13:05:45 +0200
- Subject: [PATCH] CVE-2016-4429: sunrpc: Do not use alloca in clntudp_call [BZ #20112]
- Authentication-results: sourceware.org; auth=none
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).
2016-05-19 Florian Weimer <fweimer@redhat.com>
CVE-2016-4429
[BZ #20112]
* sunrpc/clnt_udp.c (clntudp_call): Use malloc/free for the error
payload.
diff --git a/NEWS b/NEWS
index b3fd3cc..2341697 100644
--- a/NEWS
+++ b/NEWS
@@ -48,6 +48,10 @@ Security related changes:
called with the GLOB_ALTDIRFUNC flag and encountered a long file name.
Reported by Alexander Cherepanov. (CVE-2016-1234)
+* 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)
+
The following bugs are resolved with this release:
[The release manager will add the list generated by
diff --git a/sunrpc/clnt_udp.c b/sunrpc/clnt_udp.c
index a6cf5f1..4d9acb1 100644
--- a/sunrpc/clnt_udp.c
+++ b/sunrpc/clnt_udp.c
@@ -388,9 +388,15 @@ 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;
@@ -415,10 +421,12 @@ 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