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authorPhillip Lougher <phillip@squashfs.org.uk>2012-03-09 03:02:59 +0000
committerPhillip Lougher <phillip@squashfs.org.uk>2012-03-10 03:01:02 +0000
commit4b0180a49f08dd1c681cdc99edc9e0cec0a833fa (patch)
tree816d9a9095b816683c8edc2089d510880fd59d35
parent2158d3fd2769546cd9004eaeb776fee946155238 (diff)
Squashfs: add mount time sanity check for block_size and block_log match
Squashfs currently has a sanity check for block_size less than or equal to the maximum block_size (1 Mbyte). This catches some superblock corruption, but obviously with a block_size maximum of 1 Mbyte there's 7 correct values (4K, 8K, 16K, 32K, ... etc) and a lot of incorrect values which are not caught by this check. The Squashfs superblock, however, has both a block_size and a block_log (2^block_log == block_size). Checking that the block_size matches the block_log is a much more robust check. Corruption of the superblock is unlikely to produce values which match, and it also ensures the block_size is an exact power of two. Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
-rw-r--r--fs/squashfs/super.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index ecaa2f7bdb8..a55a9c57be1 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -158,10 +158,15 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
goto failed_mount;
}
+ /* Check block log for sanity */
msblk->block_log = le16_to_cpu(sblk->block_log);
if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
goto failed_mount;
+ /* Check that block_size and block_log match */
+ if (msblk->block_size != (1 << msblk->block_log))
+ goto failed_mount;
+
/* Check the root inode for sanity */
root_inode = le64_to_cpu(sblk->root_inode);
if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)