From bc779a1a5b3035133024b21e2f339fe4219fb11c Mon Sep 17 00:00:00 2001 From: Florian Weimer 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 --- ChangeLog | 7 +++++++ NEWS | 4 ++++ sunrpc/clnt_udp.c | 10 +++++++++- 3 files changed, 20 insertions(+), 1 deletion(-) Index: git/NEWS =================================================================== --- git.orig/NEWS +++ git/NEWS @@ -110,6 +110,10 @@ Security related changes: reporting the security impact of this issue, and Robert Holiday of Ciena for reporting the related bug 18665. (CVE-2015-7547) +* 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: [89] localedata: Locales nb_NO and nn_NO should transliterate æøå Index: git/sunrpc/clnt_udp.c =================================================================== --- git.orig/sunrpc/clnt_udp.c +++ git/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 Index: git/ChangeLog =================================================================== --- git.orig/ChangeLog +++ git/ChangeLog @@ -1,3 +1,10 @@ +2016-05-23 Florian Weimer + + CVE-2016-4429 + [BZ #20112] + * sunrpc/clnt_udp.c (clntudp_call): Use malloc/free for the error + payload. + 2016-04-29 Florian Weimer [BZ #20010]