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grub-editenv: Warn a user against editing environment block

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The environment block is a preallocated 1024-byte file which serves as
persistent storage for environment variables. It has its own format
which is sensitive to corruption if an editor does not know how to
process it. Besides that the editor may inadvertently change grubenv
file size and/or make it sparse which can lead to unexpected results.

This patch adds a message to the grubenv file to warn a user against
editing it by tools other than grub-editenv.

Signed-off-by: Michael Chang <mchang@suse.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Michael Chang 2019-11-05 09:20:22 +00:00 committed by Daniel Kiper
parent 42acdd3b40
commit 5e5a15872d
1 changed files with 9 additions and 5 deletions
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14
util/editenv.c
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@ -30,13 +30,13 @@
#include <string.h>
#define DEFAULT_ENVBLK_SIZE 1024
#define GRUB_ENVBLK_MESSAGE "# WARNING: Do not edit this file by tools other than "PACKAGE"-editenv!!!\n"
void
grub_util_create_envblk_file (const char *name)
{
FILE *fp;
char *buf;
char *namenew;
char *buf, *pbuf, *namenew;
buf = xmalloc (DEFAULT_ENVBLK_SIZE);
@ -46,9 +46,13 @@ grub_util_create_envblk_file (const char *name)
grub_util_error (_("cannot open `%s': %s"), namenew,
strerror (errno));
memcpy (buf, GRUB_ENVBLK_SIGNATURE, sizeof (GRUB_ENVBLK_SIGNATURE) - 1);
memset (buf + sizeof (GRUB_ENVBLK_SIGNATURE) - 1, '#',
DEFAULT_ENVBLK_SIZE - sizeof (GRUB_ENVBLK_SIGNATURE) + 1);
pbuf = buf;
memcpy (pbuf, GRUB_ENVBLK_SIGNATURE, sizeof (GRUB_ENVBLK_SIGNATURE) - 1);
pbuf += sizeof (GRUB_ENVBLK_SIGNATURE) - 1;
memcpy (pbuf, GRUB_ENVBLK_MESSAGE, sizeof (GRUB_ENVBLK_MESSAGE) - 1);
pbuf += sizeof (GRUB_ENVBLK_MESSAGE) - 1;
memset (pbuf , '#',
DEFAULT_ENVBLK_SIZE - sizeof (GRUB_ENVBLK_SIGNATURE) - sizeof (GRUB_ENVBLK_MESSAGE) + 2);
if (fwrite (buf, 1, DEFAULT_ENVBLK_SIZE, fp) != DEFAULT_ENVBLK_SIZE)
grub_util_error (_("cannot write to `%s': %s"), namenew,