[PATCH 4.9 068/101] btrfs: Check if item pointer overlaps with the item itself

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Qu Wenruo <quwenruo.btrfs@xxxxxxx>

commit 7f43d4affb2a254d421ab20b0cf65ac2569909fb upstream.

Function check_leaf() checks if any item pointer points outside of the
leaf, but it doesn't check if the pointer overlaps with the item itself.

Normally only the last item may be the victim, but adding such check is
never a bad idea anyway.

Signed-off-by: Qu Wenruo <quwenruo.btrfs@xxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/btrfs/disk-io.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -637,6 +637,13 @@ static noinline int check_leaf(struct bt
 			return -EUCLEAN;
 		}
 
+		/* Also check if the item pointer overlaps with btrfs item. */
+		if (btrfs_item_nr_offset(slot) + sizeof(struct btrfs_item) >
+		    btrfs_item_ptr_offset(leaf, slot)) {
+			CORRUPT("slot overlap with its data", leaf, root, slot);
+			return -EUCLEAN;
+		}
+
 		prev_key.objectid = key.objectid;
 		prev_key.type = key.type;
 		prev_key.offset = key.offset;