[PATCH v2 1/2] Add grub_util_readlink()

[PATCH v2 1/2] Add grub_util_readlink()

[Javier Martinez Canillas]

From: Peter Jones <pjones@redhat.com>

Currently grub-editenv and related tools are not able to follow symbolic
links when finding their config file. For example the grub-editenv create
command will wrongly overwrite a symlink in /boot/grub2/grubenv with a new
regular file, instead of creating a file in the path the symlink points to.

A following patch will change that and add support in grub-editenv to
follow symbolic links when finding the grub environment variables file.

Add a grub_util_readlink() helper function that is just a wrapper around
the platform specific function to read the value of a symbolic link. This
helper function will be used by the following patch for grub-editenv.

Signed-off-by: Peter Jones <pjones@redhat.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

---

Changes in v2:
- Add a better commit message explaining why the change is needed.
- Add Reviewed-by tag from Daniel Kiper.

 grub-core/osdep/windows/hostdisk.c    | 6 ++++++
 include/grub/osdep/hostfile_aros.h    | 6 ++++++
 include/grub/osdep/hostfile_unix.h    | 6 ++++++
 include/grub/osdep/hostfile_windows.h | 2 ++
 4 files changed, 20 insertions(+)

diff --git grub-core/osdep/windows/hostdisk.c grub-core/osdep/windows/hostdisk.c
index 355100789a7..87a106c9b82 100644
--- grub-core/osdep/windows/hostdisk.c
+++ grub-core/osdep/windows/hostdisk.c
@@ -365,6 +365,12 @@ grub_util_mkdir (const char *dir)
   free (windows_name);
 }
 
+ssize_t
+grub_util_readlink (const char *name, char *buf, size_t bufsize)
+{
+  return readlink(name, buf, bufsize);
+}
+
 int
 grub_util_rename (const char *from, const char *to)
 {
diff --git include/grub/osdep/hostfile_aros.h include/grub/osdep/hostfile_aros.h
index a059c0fa40a..161fbb7bdfd 100644
--- include/grub/osdep/hostfile_aros.h
+++ include/grub/osdep/hostfile_aros.h
@@ -68,6 +68,12 @@ grub_util_rename (const char *from, const char *to)
   return rename (from, to);
 }
 
+static inline ssize_t
+grub_util_readlink (const char *name, char *buf, size_t bufsize)
+{
+  return readlink(name, buf, bufsize);
+}
+
 #define grub_util_mkdir(a) mkdir ((a), 0755)
 
 struct grub_util_fd
diff --git include/grub/osdep/hostfile_unix.h include/grub/osdep/hostfile_unix.h
index 9ffe46fa3ca..17cd3aa8b30 100644
--- include/grub/osdep/hostfile_unix.h
+++ include/grub/osdep/hostfile_unix.h
@@ -71,6 +71,12 @@ grub_util_rename (const char *from, const char *to)
   return rename (from, to);
 }
 
+static inline ssize_t
+grub_util_readlink (const char *name, char *buf, size_t bufsize)
+{
+  return readlink(name, buf, bufsize);
+}
+
 #define grub_util_mkdir(a) mkdir ((a), 0755)
 
 #if defined (__NetBSD__)
diff --git include/grub/osdep/hostfile_windows.h include/grub/osdep/hostfile_windows.h
index bf6451b6db4..8c92d0591bb 100644
--- include/grub/osdep/hostfile_windows.h
+++ include/grub/osdep/hostfile_windows.h
@@ -41,6 +41,8 @@ typedef struct grub_util_fd_dir *grub_util_fd_dir_t;
 
 int
 grub_util_rename (const char *from, const char *to);
+ssize_t
+grub_util_readlink (const char *name, char *buf, size_t bufsize);
 int
 grub_util_unlink (const char *name);
 void
-- 
2.21.0

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

[Javier Martinez Canillas]

From: Peter Jones <pjones@redhat.com>

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 <pjones@redhat.com>
Signed-off-by: Jonathan Lebon <jlebon@redhat.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

---

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);
 
   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);
+      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);
+          const char *dir = dirname (dbuf);
+          free (rename_target);
+          rename_target = xasprintf ("%s/%s", dir, linkbuf);
+          free (dbuf);
+        }
+    }
+
+  rc = grub_util_rename (namenew, rename_target);
+  if (rc < 0 && errno == EXDEV)
+    {
+      rc = grub_install_copy_file (namenew, rename_target, 1);
+      grub_util_unlink (namenew);
+    }
+
+  if (rc < 0)
+    grub_util_error (_("cannot rename the file %s to %s: %m"), namenew, name);
+
   free (namenew);
+  free (rename_target);
 }
-- 
2.21.0

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 <pjones@redhat.com>
>
> 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 <pjones@redhat.com>
> Signed-off-by: Jonathan Lebon <jlebon@redhat.com>
> Reviewed-by: Adam Jackson <ajax@redhat.com>
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
>
> ---
>
> 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

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

[Javier Martinez Canillas]

Hello Daniel,

Thanks a lot for pointing out these issues. I'll fix them in v2.

>> +
>> +      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.
> 

Yes, I'll be more careful when reviewing our downstream patches before posting.

Best regards,
-- 
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat

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

[Javier Martinez Canillas]

Hello Daniel,

On 10/28/19 5:12 PM, Daniel Kiper wrote:
> On Mon, Oct 28, 2019 at 02:11:10PM +0100, Javier Martinez Canillas wrote:
>> From: Peter Jones <pjones@redhat.com>

[snip]

>>  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?
>

I've looked at this and it's not possible for rename_target to be NULL since
xstrdup() calls xmalloc() to allocate memory and this function already checks
if the returned pointer is NULL and calls grub_util_error() if that's the case
which exits after printing an error message.

So the code is correct and in fact I see that all xstrdup() callers (or for
any other x* function that makes allocations) don't check the return value.

>>    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

Ok, will add spaces around the + operator.

> any patch which does not check for NULL for malloc() et consortes.
>

Same, all callers of xmalloc() don't check this since as mentioned the function
already takes care of this.

>> +      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?
>

Same than above.

>> +          const char *dir = dirname (dbuf);
> 
> Empty line please...
>

Ok.

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

Same than above.

> Daniel
> 

Best regards,
-- 
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat