disk: gpt: verify alternate LBA points to last usable LBA

The gpt command require the GPT backup header at the standard location at the end of the device. Check the alternate LBA value before reading the GPT backup header from the last usable LBA of the device. Signed-off-by: Stefan Herbrechtsmeier <[email protected]> Reviewed-by: Heinrich Schuchardt <[email protected]>
PeterCxy · Apr 12, 2021 · d469338 · d469338
1 parent b935d19
commit d469338
Showing 1 changed file with 9 additions and 0 deletions.
diff --git a/disk/part_efi.c b/disk/part_efi.c
@@ -692,6 +692,15 @@ int gpt_verify_headers(struct blk_desc *dev_desc, gpt_header *gpt_head,
 	/* Free pte before allocating again */
 	free(*gpt_pte);
 
+	/*
+	 * Check that the alternate_lba entry points to the last LBA
+	 */
+	if (le64_to_cpu(gpt_head->alternate_lba) != (dev_desc->lba - 1)) {
+		printf("%s: *** ERROR: Misplaced Backup GPT ***\n",
+		       __func__);
+		return -1;
+	}
+
 	if (is_gpt_valid(dev_desc, (dev_desc->lba - 1),
 			 gpt_head, gpt_pte) != 1) {
 		printf("%s: *** ERROR: Invalid Backup GPT ***\n",