[PATCH v3] resolv/nss_dns/dns-host: Get rid of alloca.

[Joe Simmons-Talbott]

On Mon, Aug 14, 2023 at 10:28:07AM -0400, Siddhesh Poyarekar wrote:
> On 2023-08-14 10:23, Andreas Schwab via Libc-alpha wrote:
> > On Aug 14 2023, Joe Simmons-Talbott via Libc-alpha wrote:
> > 
> > > diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
> > > index 1d60c51f5e..160a017d42 100644
> > > --- a/resolv/nss_dns/dns-host.c
> > > +++ b/resolv/nss_dns/dns-host.c
> > > @@ -395,8 +395,8 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
> > >      */
> > >     if (strchr (name, '.') == NULL)
> > >       {
> > > -      char *tmp = alloca (NS_MAXDNAME);
> > > -      const char *cp = __res_context_hostalias (ctx, name, tmp, NS_MAXDNAME);
> > > +      char tmp[NS_MAXDNAME];
> > > +      const char *cp = __res_context_hostalias (ctx, name, tmp, sizeof (tmp));
> > >         if (cp != NULL)
> > >   	name = cp;
> > >       }
> > 
> > We don't tolerate undefined behaviour in glibc.
> > 
> 
> Ah, sorry I hadn't noticed that cp escapes that scope.  Joe, your v2 is
> correct.

I went ahead and posted a v4 patch moving tmp back up one scope level
[1]

[1] https://sourceware.org/pipermail/libc-alpha/2023-August/150906.html

Thanks,
Joe