Re: [PATCH] CVE-2018-19591: if_nametoindex: Fix descriptor for overlong name [BZ #23927]

[Victor Rodriguez <vm dot rod25 at gmail dot com>]

On Tue, Nov 27, 2018 at 9:13 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * Andreas Schwab:
>
> > On Nov 27 2018, Florian Weimer <fweimer@redhat.com> wrote:
> >
> >> diff --git a/sysdeps/unix/sysv/linux/if_index.c b/sysdeps/unix/sysv/linux/if_index.c
> >> index e3d08982d9..3e999d6509 100644
> >> --- a/sysdeps/unix/sysv/linux/if_index.c
> >> +++ b/sysdeps/unix/sysv/linux/if_index.c
> >> @@ -45,6 +45,7 @@ __if_nametoindex (const char *ifname)
> >>
> >>    if (strlen (ifname) >= IFNAMSIZ)
> >>      {
> >> +      __close_nocancel_nostatus (fd);
> >>        __set_errno (ENODEV);
> >>        return 0;
> >>      }
> >
> > Just move it before the opensock call.
>
> Like this?
>
> 2018-11-27  Florian Weimer  <fweimer@redhat.com>
>
>         [BZ #23927]
>         CVE-2018-19591
>         * sysdeps/unix/sysv/linux/if_index.c (__if_nametoindex): Avoid
>         descriptor leak in case of ENODEV error.
>
> diff --git a/NEWS b/NEWS
> index f488821af1..1098be1afb 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -57,7 +57,9 @@ Changes to build and runtime requirements:
>
>  Security related changes:
>
> -  [Add security related changes here]
> +  CVE-2018-19591: A file descriptor leak in if_nametoindex can lead to a
> +  denial of service due to resource exhaustion when processing getaddrinfo
> +  calls with crafted host names.  Reported by Guido Vranken.
>
>  The following bugs are resolved with this release:
>
> diff --git a/sysdeps/unix/sysv/linux/if_index.c b/sysdeps/unix/sysv/linux/if_index.c
> index e3d08982d9..782fc5e175 100644
> --- a/sysdeps/unix/sysv/linux/if_index.c
> +++ b/sysdeps/unix/sysv/linux/if_index.c
> @@ -38,11 +38,6 @@ __if_nametoindex (const char *ifname)
>    return 0;
>  #else
>    struct ifreq ifr;
> -  int fd = __opensock ();
> -
> -  if (fd < 0)
> -    return 0;
> -
>    if (strlen (ifname) >= IFNAMSIZ)
>      {
>        __set_errno (ENODEV);
> @@ -50,6 +45,12 @@ __if_nametoindex (const char *ifname)
>      }
>
>    strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
> +
> +  int fd = __opensock ();
> +
> +  if (fd < 0)
> +    return 0;
> +
>    if (__ioctl (fd, SIOCGIFINDEX, &ifr) < 0)
>      {
>        int saved_errno = errno;

Thanks for the fix, is this going to be in master?
Can we take this patch as CVE fix?