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From:   Sean Nyekjaer <sean@geanix.com>
To:     Phillip Lougher <phillip@squashfs.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Sean Nyekjaer <sean@geanix.com>, stable@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] squashfs: fix inode lookup sanity checks
Date:   Fri, 26 Feb 2021 10:29:03 +0100
Message-Id: <20210226092903.1473545-1-sean@geanix.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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.

Fixes: eabac19e40c0 ("squashfs: add more sanity checks in inode lookup")
CC: stable@vger.kernel.org
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
---
 fs/squashfs/export.c      | 8 ++++++--
 fs/squashfs/squashfs_fs.h | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/squashfs/export.c b/fs/squashfs/export.c
index eb02072d28dd..723763746238 100644
--- a/fs/squashfs/export.c
+++ b/fs/squashfs/export.c
@@ -152,14 +152,18 @@ __le64 *squashfs_read_inode_lookup_table(struct super_block *sb,
 		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);
 	}
diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
index 8d64edb80ebf..b3fdc8212c5f 100644
--- a/fs/squashfs/squashfs_fs.h
+++ b/fs/squashfs/squashfs_fs.h
@@ -17,6 +17,7 @@
 
 /* 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
-- 
2.29.2