| Message ID | 20160519110545.ED146400FD12E@oldenburg.str.redhat.com |
|---|---|
| State | New |
| Headers | show |
fweimer@redhat.com (Florian Weimer) writes: > 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). If you use a VLA you can avoid that. Andreas.
On 05/19/2016 01:53 PM, Andreas Schwab wrote: > fweimer@redhat.com (Florian Weimer) writes: > >> 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). > > If you use a VLA you can avoid that. It's still a maintenance hazard for libtirpc because they might eventually support IPv6 jumbograms, which won't fit on the stack. Florian
I want to commit the original patch later today. Thanks, Florian
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