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CVE-2016-4429: sunrpc: Do not use alloca in clntudp_call [BZ #20112]

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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).
This commit is contained in:
Florian Weimer 2016-05-23 20:18:34 +02:00
parent 3375cfafa7
commit bc779a1a5b
3 changed files with 20 additions and 1 deletions
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7
ChangeLog
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@ -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.
2016-05-23 Florian Weimer <fweimer@redhat.com> 2016-05-23 Florian Weimer <fweimer@redhat.com>
[BZ #20111] [BZ #20111]

4
NEWS
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@ -48,6 +48,10 @@ Security related changes:
called with the GLOB_ALTDIRFUNC flag and encountered a long file name. called with the GLOB_ALTDIRFUNC flag and encountered a long file name.
Reported by Alexander Cherepanov. (CVE-2016-1234) 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 following bugs are resolved with this release:
[The release manager will add the list generated by [The release manager will add the list generated by

10
sunrpc/clnt_udp.c
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@ -388,9 +388,15 @@ send_again:
struct sock_extended_err *e; struct sock_extended_err *e;
struct sockaddr_in err_addr; struct sockaddr_in err_addr;
struct iovec iov; struct iovec iov;
char *cbuf = (char *) alloca (outlen + 256); char *cbuf = malloc (outlen + 256);
int ret; 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_base = cbuf + 256;
iov.iov_len = outlen; iov.iov_len = outlen;
msg.msg_name = (void *) &err_addr; msg.msg_name = (void *) &err_addr;
@ -415,10 +421,12 @@ send_again:
cmsg = CMSG_NXTHDR (&msg, cmsg)) cmsg = CMSG_NXTHDR (&msg, cmsg))
if (cmsg->cmsg_level == SOL_IP && cmsg->cmsg_type == IP_RECVERR) if (cmsg->cmsg_level == SOL_IP && cmsg->cmsg_type == IP_RECVERR)
{ {
free (cbuf);
e = (struct sock_extended_err *) CMSG_DATA(cmsg); e = (struct sock_extended_err *) CMSG_DATA(cmsg);
cu->cu_error.re_errno = e->ee_errno; cu->cu_error.re_errno = e->ee_errno;
return (cu->cu_error.re_status = RPC_CANTRECV); return (cu->cu_error.re_status = RPC_CANTRECV);
} }
free (cbuf);
} }
#endif #endif
do do