[PATCH v2 22/22] Squashfs: check index isn't greater than S64_MAX in squashfs_read_data()

[Phillip Lougher <phillip@squashfs.org.uk>]

The previous commits in this patch-set now sanity check index before
squashfs_read_data() is called.  However, it is always wise to take
a belts and braces approach and sanity check at the lowest level to
trap any values that could slip through.

Fixes: e2780ab159ac6 ("Squashfs: block operations")
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
---
 fs/squashfs/block.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
index 20c3030b4f96..f2f03d815167 100644
--- a/fs/squashfs/block.c
+++ b/fs/squashfs/block.c
@@ -297,6 +297,15 @@ int squashfs_read_data(struct super_block *sb, u64 index, int length,
 	int res;
 	int offset;
 
+	/*
+	 * Reject index values greater than possible filesystem size (S64_MAX).
+	 * This also ensures the index variable doesn't overflow in the function.
+	 */
+	if (index > S64_MAX) {
+		res = -EIO;
+		goto out;
+	}
+
 	if (length) {
 		/*
 		 * Datablock.
-- 
2.47.3