fs/tar: Integer overflow leads to heap OOB write

Both namesize and linksize are derived from hd.size, a 12-digit octal
number parsed by read_number(). Later direct arithmetic calculation like
"namesize + 1" and "linksize + 1" may exceed the maximum value of
grub_size_t leading to heap OOB write. This patch fixes the issue by
using grub_add() and checking for an overflow.

Fixes: CVE-2024-45780
Reported-by: Nils Langius <nils@langius.de>
Signed-off-by: Lidong Chen <lidong.chen@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Alec Brown <alec.r.brown@oracle.com>

diff --git a/grub-core/fs/tar.c b/grub-core/fs/tar.c
index 646bce5ebf68ac1240e9776e38a86dcc2a1f2608..386c090226f13f1601f25711715ea5bf6bbad4ce 100644 (file)
--- a/grub-core/fs/tar.c
+++ b/grub-core/fs/tar.c
@@ -25,6 +25,7 @@
 #include <grub/mm.h>
 #include <grub/dl.h>
 #include <grub/i18n.h>
+#include <grub/safemath.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -76,6 +77,7 @@ grub_cpio_find_file (struct grub_archelp_data *data, char **name,
 {
   struct head hd;
   int reread = 0, have_longname = 0, have_longlink = 0;
+  grub_size_t sz;
 
   data->hofs = data->next_hofs;
   *name = NULL;
@@ -98,7 +100,11 @@ grub_cpio_find_file (struct grub_archelp_data *data, char **name,
        {
          grub_err_t err;
          grub_size_t namesize = read_number (hd.size, sizeof (hd.size));
-         *name = grub_malloc (namesize + 1);
+
+         if (grub_add (namesize, 1, &sz))
+           return grub_error (GRUB_ERR_BAD_FS, N_("name size overflow"));
+
+         *name = grub_malloc (sz);
          if (*name == NULL)
            return grub_errno;
          err = grub_disk_read (data->disk, 0,
@@ -118,15 +124,19 @@ grub_cpio_find_file (struct grub_archelp_data *data, char **name,
        {
          grub_err_t err;
          grub_size_t linksize = read_number (hd.size, sizeof (hd.size));
-         if (data->linkname_alloc < linksize + 1)
+
+         if (grub_add (linksize, 1, &sz))
+           return grub_error (GRUB_ERR_BAD_FS, N_("link size overflow"));
+
+         if (data->linkname_alloc < sz)
            {
              char *n;
-             n = grub_calloc (2, linksize + 1);
+             n = grub_calloc (2, sz);
              if (!n)
                return grub_errno;
              grub_free (data->linkname);
              data->linkname = n;
-             data->linkname_alloc = 2 * (linksize + 1);
+             data->linkname_alloc = 2 * (sz);
            }
 
          err = grub_disk_read (data->disk, 0,
@@ -149,7 +159,10 @@ grub_cpio_find_file (struct grub_archelp_data *data, char **name,
          while (extra_size < sizeof (hd.prefix)
                 && hd.prefix[extra_size])
            extra_size++;
-         *name = grub_malloc (sizeof (hd.name) + extra_size + 2);
+
+         if (grub_add (sizeof (hd.name) + 2, extra_size, &sz))
+           return grub_error (GRUB_ERR_BAD_FS, N_("long name size overflow"));
+         *name = grub_malloc (sz);
          if (*name == NULL)
            return grub_errno;
          if (hd.prefix[0])