[PATCH 4.9 18/53] squashfs: fix inode lookup sanity checks

[Greg Kroah-Hartman]

From: Sean Nyekjaer <sean@xxxxxxxxxx>

commit c1b2028315c6b15e8d6725e0d5884b15887d3daa upstream.

When mouting a squashfs image created without inode compression it fails
with: "unable to read inode lookup table"

It turns out that the BLOCK_OFFSET is missing when checking the
SQUASHFS_METADATA_SIZE agaist the actual size.

Link: https://lkml.kernel.org/r/20210226092903.1473545-1-sean@xxxxxxxxxx
Fixes: eabac19e40c0 ("squashfs: add more sanity checks in inode lookup")
Signed-off-by: Sean Nyekjaer <sean@xxxxxxxxxx>
Acked-by: Phillip Lougher <phillip@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/squashfs/export.c      |    8 ++++++--
 fs/squashfs/squashfs_fs.h |    1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

--- a/fs/squashfs/export.c
+++ b/fs/squashfs/export.c
@@ -165,14 +165,18 @@ __le64 *squashfs_read_inode_lookup_table
 		start = le64_to_cpu(table[n]);
 		end = le64_to_cpu(table[n + 1]);
 
-		if (start >= end || (end - start) > SQUASHFS_METADATA_SIZE) {
+		if (start >= end
+		    || (end - start) >
+		    (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
 			kfree(table);
 			return ERR_PTR(-EINVAL);
 		}
 	}
 
 	start = le64_to_cpu(table[indexes - 1]);
-	if (start >= lookup_table_start || (lookup_table_start - start) > SQUASHFS_METADATA_SIZE) {
+	if (start >= lookup_table_start ||
+	    (lookup_table_start - start) >
+	    (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
 		kfree(table);
 		return ERR_PTR(-EINVAL);
 	}
--- a/fs/squashfs/squashfs_fs.h
+++ b/fs/squashfs/squashfs_fs.h
@@ -30,6 +30,7 @@
 
 /* size of metadata (inode and directory) blocks */
 #define SQUASHFS_METADATA_SIZE		8192
+#define SQUASHFS_BLOCK_OFFSET		2
 
 /* default size of block device I/O */
 #ifdef CONFIG_SQUASHFS_4K_DEVBLK_SIZE