Blame SOURCES/0454-disk-lvm-Don-t-blast-past-the-end-of-the-circular-me.patch

468bd4
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
468bd4
From: Daniel Axtens <dja@axtens.net>
468bd4
Date: Thu, 21 Jan 2021 18:19:51 +1100
468bd4
Subject: [PATCH] disk/lvm: Don't blast past the end of the circular metadata
468bd4
 buffer
468bd4
468bd4
This catches at least some OOB reads, and it's possible I suppose that
468bd4
if 2 * mda_size is less than GRUB_LVM_MDA_HEADER_SIZE it might catch some
468bd4
OOB writes too (although that hasn't showed up as a crash in fuzzing yet).
468bd4
468bd4
It's a bit ugly and I'd appreciate better suggestions.
468bd4
468bd4
Signed-off-by: Daniel Axtens <dja@axtens.net>
468bd4
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
468bd4
---
468bd4
 grub-core/disk/lvm.c | 10 ++++++++++
468bd4
 1 file changed, 10 insertions(+)
468bd4
468bd4
diff --git a/grub-core/disk/lvm.c b/grub-core/disk/lvm.c
09e3cc
index 0f466040a..ec3545e16 100644
468bd4
--- a/grub-core/disk/lvm.c
468bd4
+++ b/grub-core/disk/lvm.c
468bd4
@@ -215,6 +215,16 @@ grub_lvm_detect (grub_disk_t disk,
468bd4
   if (grub_le_to_cpu64 (rlocn->offset) + grub_le_to_cpu64 (rlocn->size) >
468bd4
       grub_le_to_cpu64 (mdah->size))
468bd4
     {
468bd4
+      if (2 * mda_size < GRUB_LVM_MDA_HEADER_SIZE ||
468bd4
+          (grub_le_to_cpu64 (rlocn->offset) + grub_le_to_cpu64 (rlocn->size) -
468bd4
+	   grub_le_to_cpu64 (mdah->size) > mda_size - GRUB_LVM_MDA_HEADER_SIZE))
468bd4
+	{
468bd4
+#ifdef GRUB_UTIL
468bd4
+	  grub_util_info ("cannot copy metadata wrap in circular buffer");
468bd4
+#endif
468bd4
+	  goto fail2;
468bd4
+	}
468bd4
+
468bd4
       /* Metadata is circular. Copy the wrap in place. */
468bd4
       grub_memcpy (metadatabuf + mda_size,
468bd4
 		   metadatabuf + GRUB_LVM_MDA_HEADER_SIZE,