lkml.org 
[lkml]   [2012]   [Mar]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 6/6] 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>
---
fs/squashfs/super.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index ecaa2f7..a55a9c5 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)
--
1.7.5.4


\
 
 \ /
  Last update: 2012-03-10 03:59    [W:0.045 / U:0.600 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site