1From 27a79bf38e6d050e497eb96a3fdddce43af25577 Mon Sep 17 00:00:00 2001
2From: Daniel Axtens <dja@axtens.net>
3Date: Thu, 21 Jan 2021 18:19:51 +1100
4Subject: [PATCH] disk/lvm: Don't blast past the end of the circular metadata
5 buffer
6
7This catches at least some OOB reads, and it's possible I suppose that
8if 2 * mda_size is less than GRUB_LVM_MDA_HEADER_SIZE it might catch some
9OOB writes too (although that hasn't showed up as a crash in fuzzing yet).
10
11It's a bit ugly and I'd appreciate better suggestions.
12
13Signed-off-by: Daniel Axtens <dja@axtens.net>
14Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
15Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
16---
17 grub-core/disk/lvm.c | 10 ++++++++++
18 1 file changed, 10 insertions(+)
19
20diff --git a/grub-core/disk/lvm.c b/grub-core/disk/lvm.c
21index 8136122..36da575 100644
22--- a/grub-core/disk/lvm.c
23+++ b/grub-core/disk/lvm.c
24@@ -214,6 +214,16 @@ grub_lvm_detect (grub_disk_t disk,
25   if (grub_le_to_cpu64 (rlocn->offset) + grub_le_to_cpu64 (rlocn->size) >
26       grub_le_to_cpu64 (mdah->size))
27     {
28+      if (2 * mda_size < GRUB_LVM_MDA_HEADER_SIZE ||
29+          (grub_le_to_cpu64 (rlocn->offset) + grub_le_to_cpu64 (rlocn->size) -
30+	   grub_le_to_cpu64 (mdah->size) > mda_size - GRUB_LVM_MDA_HEADER_SIZE))
31+	{
32+#ifdef GRUB_UTIL
33+	  grub_util_info ("cannot copy metadata wrap in circular buffer");
34+#endif
35+	  goto fail2;
36+	}
37+
38       /* Metadata is circular. Copy the wrap in place. */
39       grub_memcpy (metadatabuf + mda_size,
40 		   metadatabuf + GRUB_LVM_MDA_HEADER_SIZE,
41--
422.14.2
43
44