partitions/efi: compare first and last usable LBAs

When verifying GPT header integrity, make sure that first usable LBA is
smaller than last usable LBA.

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Reviewed-by: Karel Zak <kzak@redhat.com>
Acked-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/block/partitions/efi.c b/block/partitions/efi.c
index b028af688361..de9f9bfa24bc 100644
--- a/block/partitions/efi.c
+++ b/block/partitions/efi.c
@@ -410,7 +410,12 @@ static int is_gpt_valid(struct parsed_partitions *state, u64 lba,
                          (unsigned long long)lastlba);
                 goto fail;
         }
-
+        if (le64_to_cpu((*gpt)->last_usable_lba) < le64_to_cpu((*gpt)->first_usable_lba)) {
+                pr_debug("GPT: last_usable_lba incorrect: %lld > %lld\n",
+                         (unsigned long long)le64_to_cpu((*gpt)->last_usable_lba),
+                         (unsigned long long)le64_to_cpu((*gpt)->first_usable_lba));
+                goto fail;
+        }
         /* Check that sizeof_partition_entry has the correct value */
         if (le32_to_cpu((*gpt)->sizeof_partition_entry) != sizeof(gpt_entry)) {
                 pr_debug("GUID Partitition Entry Size check failed.\n");