[Libguestfs] [PATCH] inspect: resolve symlinks when detecting architecture

[Richard W.M. Jones]

On Tue, Jan 26, 2016 at 06:49:55PM +0100, Pino Toscano wrote:
> Resolve the paths of the binaries we are looking in the guest to
> identify the architecture. This way we can identify also busybox-based
> guests such as Alpine Linux, where all the "base" binaries in /bin are
> symlinks to busybox.
> ---
>  src/inspect-fs-unix.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/src/inspect-fs-unix.c b/src/inspect-fs-unix.c
> index f915e86..75c76f8 100644
> --- a/src/inspect-fs-unix.c
> +++ b/src/inspect-fs-unix.c
> @@ -1082,10 +1082,22 @@ check_architecture (guestfs_h *g, struct inspect_fs *fs)
>    char *arch;
>  
>    for (i = 0; i < sizeof binaries / sizeof binaries[0]; ++i) {
> -    if (guestfs_is_file (g, binaries[i]) > 0) {
> -      /* Ignore errors from file_architecture call. */
> +    /* Allow symlinks when checking the binaries:,so in case they are
> +     * relative ones (which can be resolved within the same partition),
> +     * then we can check the architecture of their target.
> +     */
> +    if (guestfs_is_file_opts (g, binaries[i],
> +                              GUESTFS_IS_FILE_OPTS_FOLLOWSYMLINKS, 1, -1) > 0) {
> +      CLEANUP_FREE char *resolved = NULL;
> +
> +      /* Ignore errors from realpath and file_architecture calls. */
>        guestfs_push_error_handler (g, NULL, NULL);
> -      arch = guestfs_file_architecture (g, binaries[i]);
> +      resolved = guestfs_realpath (g, binaries[i]);
> +      /* If is_file above succeeded realpath should too, but better
> +       * be safe than sorry.
> +       */
> +      if (resolved)
> +        arch = guestfs_file_architecture (g, resolved);
>        guestfs_pop_error_handler (g);
>  
>        if (arch) {

Thanks - *Pushed*, *but* I changed the patch so that 'char *arch =
NULL', else there's a possibility of accessing an uninitialized
pointer.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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