Re: [PATCH v2 2/2] Make editenv chase symlinks including those across devices

[Daniel Kiper]

On Mon, Oct 28, 2019 at 02:11:10PM +0100, Javier Martinez Canillas wrote:
> From: Peter Jones <address@hidden>
>
> The grub-editenv create command will wrongly overwrite /boot/grub2/grubenv
> with a regular file if grubenv is a symbolic link. But instead, it should
> create a new file in the path the symlink points to.
>
> This lets /boot/grub2/grubenv be a symlink to /boot/efi/EFI/fedora/grubenv
> even when they're different mount points, which allows grub2-editenv to be
> the same across platforms (i.e. UEFI vs BIOS).
>
> For example, in Fedora the GRUB EFI builds have prefix set to /EFI/fedora
> (on the EFI System Partition), but for BIOS machine it'll be /boot/grub2
> (which may or may not be its own mountpoint).
>
> With this patch, on EFI machines we can make /boot/grub2/grubenv a symlink
> to /boot/efi/EFI/fedora/grubenv, and the same copy of grub-set-default will
> work on both kinds of systems.
>
> Signed-off-by: Peter Jones <address@hidden>
> Signed-off-by: Jonathan Lebon <address@hidden>
> Reviewed-by: Adam Jackson <address@hidden>
> Signed-off-by: Javier Martinez Canillas <address@hidden>
>
> ---
>
> Changes in v2:
> - Address issues pointed out by Daniel Kiper in the previous version.
>
>  Makefile.util.def | 11 +++++++++
>  util/editenv.c    | 59 +++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 68 insertions(+), 2 deletions(-)
>
> diff --git Makefile.util.def Makefile.util.def
> index 969d32f0097..733a397cb2b 100644
> --- Makefile.util.def
> +++ Makefile.util.def
> @@ -240,8 +240,19 @@ program = {
>
>    common = util/grub-editenv.c;
>    common = util/editenv.c;
> +  common = util/grub-install-common.c;
>    common = grub-core/osdep/init.c;
> +  common = grub-core/osdep/compress.c;
> +  extra_dist = grub-core/osdep/unix/compress.c;
> +  extra_dist = grub-core/osdep/basic/compress.c;
> +  common = util/mkimage.c;
> +  common = util/grub-mkimage32.c;
> +  common = util/grub-mkimage64.c;
> +  common = grub-core/osdep/config.c;
> +  common = util/config.c;
> +  common = util/resolve.c;
>
> +  ldadd = '$(LIBLZMA)';
>    ldadd = libgrubmods.a;
>    ldadd = libgrubgcry.a;
>    ldadd = libgrubkern.a;
> diff --git util/editenv.c util/editenv.c
> index eb2d0c03a98..accc08407d9 100644
> --- util/editenv.c
> +++ util/editenv.c
> @@ -28,15 +28,19 @@
>
>  #include <errno.h>
>  #include <string.h>
> +#include <libgen.h>
>
>  #define DEFAULT_ENVBLK_SIZE  1024
>
>  void
>  grub_util_create_envblk_file (const char *name)
>  {
> +  int rc;
>    FILE *fp;
>    char *buf;
>    char *namenew;
> +  ssize_t size = 1;
> +  char *rename_target = xstrdup (name);

What will happen if rename_target is NULL?

>    buf = xmalloc (DEFAULT_ENVBLK_SIZE);
>
> @@ -60,7 +64,58 @@ grub_util_create_envblk_file (const char *name)
>    free (buf);
>    fclose (fp);
>
> -  if (grub_util_rename (namenew, name) < 0)
> -    grub_util_error (_("cannot rename the file %s to %s"), namenew, name);
> +  while (1)
> +    {
> +      char *linkbuf;
> +      ssize_t retsize;
> +
> +      linkbuf = xmalloc (size+1);

Please check for NULL here. And "size + 1". In general I will not accept
any patch which does not check for NULL for malloc() et consortes.

> +      retsize = grub_util_readlink (rename_target, linkbuf, size);
> +      if (retsize < 0 && (errno == ENOENT || errno == EINVAL))
> +     {
> +       free (linkbuf);
> +       break;
> +     }
> +      else if (retsize < 0)
> +     {
> +       grub_util_error (_("cannot rename the file %s to %s: %m"), namenew, 
> name);
> +       free (linkbuf);
> +       free (namenew);
> +       return;
> +     }
> +      else if (retsize == size)
> +     {
> +       free (linkbuf);
> +       size += 128;
> +       continue;
> +     }
> +
> +      linkbuf[retsize] = '\0';
> +      if (linkbuf[0] == '/')
> +        {
> +          free (rename_target);
> +          rename_target = linkbuf;
> +        }
> +      else
> +        {
> +          char *dbuf = xstrdup (rename_target);

What happens if dbuf is NULL?

> +          const char *dir = dirname (dbuf);

Empty line please...

> +          free (rename_target);
> +          rename_target = xasprintf ("%s/%s", dir, linkbuf);

NULL?

Daniel