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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).
(cherry picked from commit bc779a1a5b3035133024b21e2f339fe4219fb11c)
---
sunrpc/clnt_udp.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/sunrpc/clnt_udp.c b/sunrpc/clnt_udp.c
index a6cf5f1ca733..4d9acb1e6a6b 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
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