0021-gpt-refuse-to-write-to-sector-0.patch

From 2ebc9802edf1656597d8f6d7f9cc557dae08d4b2 Mon Sep 17 00:00:00 2001
From: Michael Marineau <michael.marineau@coreos.com>
Date: Thu, 11 Aug 2016 15:02:21 -0700
Subject: [PATCH] gpt: refuse to write to sector 0

---
 grub-core/lib/gpt.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/grub-core/lib/gpt.c b/grub-core/lib/gpt.c
index f83fe29ac..b7449911a 100644
--- a/grub-core/lib/gpt.c
+++ b/grub-core/lib/gpt.c
@@ -626,10 +626,17 @@ grub_gpt_write_table (grub_disk_t disk, grub_gpt_t gpt,
 		       sizeof (*header));
 
   addr = grub_gpt_sector_to_addr (gpt, grub_le_to_cpu64 (header->header_lba));
+  if (addr == 0)
+    return grub_error (GRUB_ERR_BUG,
+		       "Refusing to write GPT header to address 0x0");
   if (grub_disk_write (disk, addr, 0, sizeof (*header), header))
     return grub_errno;
 
   addr = grub_gpt_sector_to_addr (gpt, grub_le_to_cpu64 (header->partitions));
+  if (addr < 2)
+    return grub_error (GRUB_ERR_BUG,
+		       "Refusing to write GPT entries to address 0x%llx",
+		       (unsigned long long) addr);
   if (grub_disk_write (disk, addr, 0, gpt->entries_size, gpt->entries))
     return grub_errno;