Re: [PATCH] ldconfig: create /var/cache/ldconfig also with -r

[Aurelien Jarno <aurelien@aurel32.net>]

On 2022-10-11 14:20, Johannes Schauer Marin Rodrigues wrote:
> Without the -r option, ldconfig creates /var/cache/ldconfig if it didn't
> exist yet. With the -r option, a non-existing /var/cache/ldconfig inside
> the chroot directory will *not* get created because chroot_canon() will
> return NULL if the path doesn't exist. This means that aux_cache_file
> will be set to NULL and save_aux_cache() doesn't get executed at the
> end. So instead of using chroot_canon() to prepending the chroot path,
> combine the paths manually.
> ---
>  elf/ldconfig.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/elf/ldconfig.c b/elf/ldconfig.c
> index e6c24e71a4..da76dc31b8 100644
> --- a/elf/ldconfig.c
> +++ b/elf/ldconfig.c
> @@ -1293,9 +1293,11 @@ main (int argc, char **argv)
>  	add_system_dir (LIBDIR);
>      }
>  
> -  const char *aux_cache_file = _PATH_LDCONFIG_AUX_CACHE;
> -  if (opt_chroot != NULL)
> -    aux_cache_file = chroot_canon (opt_chroot, aux_cache_file);
> +  char *aux_cache_file = (char *)(_PATH_LDCONFIG_AUX_CACHE);
> +  if (opt_chroot != NULL) {
> +    aux_cache_file = alloca (strlen (opt_chroot) + strlen (_PATH_LDCONFIG_AUX_CACHE) + 2);
> +    sprintf (aux_cache_file, "%s/%s", opt_chroot, _PATH_LDCONFIG_AUX_CACHE);
> +  }

This drops the use chroot_canon() call. I am afraid it might allows one
to "escape" the "chroot". Imagine that /var/cache/ldconfig is a symlink
pointing outside of the opt_chroot.

To avoid changing the code too much, one way could be to call
chroot_canon(opt_chroot, "/var/cache/ldconfig") and concatenate the
result with "aux-cache".

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net