From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@axtens.net>
Date: Fri, 22 Jan 2021 18:13:56 +1100
Subject: [PATCH] fs/hfsplus: Don't fetch a key beyond the end of the node

Otherwise you get a wild pointer, leading to a bunch of invalid reads.
Check it falls inside the given node.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/hfsplus.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/grub-core/fs/hfsplus.c b/grub-core/fs/hfsplus.c
index 03a33ea2477..423f4b956ba 100644
--- a/grub-core/fs/hfsplus.c
+++ b/grub-core/fs/hfsplus.c
@@ -635,6 +635,10 @@ grub_hfsplus_btree_search (struct grub_hfsplus_btree *btree,
 	      pointer = ((char *) currkey
 			 + grub_be_to_cpu16 (currkey->keylen)
 			 + 2);
+
+	      if ((char *) pointer > node + btree->nodesize - 2)
+		return grub_error (GRUB_ERR_BAD_FS, "HFS+ key beyond end of node");
+
 	      currnode = grub_be_to_cpu32 (grub_get_unaligned32 (pointer));
 	      match = 1;
 	    }
