From: Alexey Makhalov <amakhalov@vmware.com>
Date: Fri, 17 Jul 2020 05:17:26 +0000 (+0000)
Subject: relocator: Fix grub_relocator_alloc_chunk_align() top memory allocation
X-Git-Tag: grub-2.06-rc1~227
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=07e5b79e22fd58c5382323dd71d64aaa42f928ec;p=thirdparty%2Fgrub.git

relocator: Fix grub_relocator_alloc_chunk_align() top memory allocation

Current implementation of grub_relocator_alloc_chunk_align()
does not allow allocation of the top byte.

Assuming input args are:
  max_addr = 0xfffff000;
  size = 0x1000;

And this is valid. But following overflow protection will
unnecessarily move max_addr one byte down (to 0xffffefff):
  if (max_addr > ~size)
    max_addr = ~size;

~size + 1 will fix the situation. In addition, check size
for non zero to do not zero max_addr.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---

diff --git a/grub-core/lib/relocator.c b/grub-core/lib/relocator.c
index 5847aac36..f2c1944c2 100644
--- a/grub-core/lib/relocator.c
+++ b/grub-core/lib/relocator.c
@@ -1386,8 +1386,8 @@ grub_relocator_alloc_chunk_align (struct grub_relocator *rel,
   };
   grub_addr_t min_addr2 = 0, max_addr2;
 
-  if (max_addr > ~size)
-    max_addr = ~size;
+  if (size && (max_addr > ~size))
+    max_addr = ~size + 1;
 
 #ifdef GRUB_MACHINE_PCBIOS
   if (min_addr < 0x1000)