This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH] CVE-2016-3075: Stack overflow in _nss_dns_getnetbyname_r [BZ #19879]
- From: Carlos O'Donell <carlos at redhat dot com>
- To: Florian Weimer <fweimer at redhat dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 29 Mar 2016 09:49:28 -0400
- Subject: Re: [PATCH] CVE-2016-3075: Stack overflow in _nss_dns_getnetbyname_r [BZ #19879]
- Authentication-results: sourceware.org; auth=none
- References: <56FA607D dot 4070803 at redhat dot com>
On 03/29/2016 07:01 AM, Florian Weimer wrote:
> This is a minor security issue in nss_dns, triggered by a very long name
> passed to getnetbyname.
>
> The defensive copy is not needed because the name may not alias the
> output buffer.
This code dates back to the original 1996 sources that were included in glibc
and I expect that at that point the propagation of `const char *` for name
was not entirely complete and that at some point the internals assumed they
could scribble on name. That is not the case today, we propagate `const char *`
to all callers, and a rather deep review that I just did using ctags shows
that the call tree preserves the constness of name.
This patch looks good to me.
> 2016-03-29 Florian Weimer <fweimer@redhat.com>
>
> [BZ #19879]
> CVE-2016-3075
> * resolv/nss_dns/dns-network.c (_nss_dns_getnetbyname_r): Do not
> copy name.
>
> diff --git a/resolv/nss_dns/dns-network.c b/resolv/nss_dns/dns-network.c
> index 2eb2f67..8f301a7 100644
> --- a/resolv/nss_dns/dns-network.c
> +++ b/resolv/nss_dns/dns-network.c
> @@ -118,17 +118,14 @@ _nss_dns_getnetbyname_r (const char *name, struct netent *result,
> } net_buffer;
> querybuf *orig_net_buffer;
> int anslen;
> - char *qbuf;
> enum nss_status status;
>
> if (__res_maybe_init (&_res, 0) == -1)
> return NSS_STATUS_UNAVAIL;
>
> - qbuf = strdupa (name);
> -
> net_buffer.buf = orig_net_buffer = (querybuf *) alloca (1024);
>
> - anslen = __libc_res_nsearch (&_res, qbuf, C_IN, T_PTR, net_buffer.buf->buf,
> + anslen = __libc_res_nsearch (&_res, name, C_IN, T_PTR, net_buffer.buf->buf,
> 1024, &net_buffer.ptr, NULL, NULL, NULL, NULL);
> if (anslen < 0)
> {
--
Cheers,
Carlos.