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Subject[099/105] Squashfs: handle corruption of directory structure
2.6.38-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Phillip Lougher <phillip@lougher.demon.co.uk>

commit 44cff8a9ee8a974f9e931df910688e7fc1f0b0f9 upstream.

Handle the rare case where a directory metadata block is uncompressed and
corrupted, leading to a kernel oops in directory scanning (memcpy).
Normally corruption is detected at the decompression stage and dealt with
then, however, this will not happen if:

- metadata isn't compressed (users can optionally request no metadata
compression), or
- the compressed metadata block was larger than the original, in which
case the uncompressed version was used, or
- the data was corrupt after decompression

This patch fixes this by adding some sanity checks against known maximum
values.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/squashfs/dir.c | 9 +++++++++
fs/squashfs/namei.c | 12 ++++++++++++
2 files changed, 21 insertions(+)
--- a/fs/squashfs/dir.c
+++ b/fs/squashfs/dir.c
@@ -172,6 +172,11 @@ static int squashfs_readdir(struct file
length += sizeof(dirh);

dir_count = le32_to_cpu(dirh.count) + 1;
+
+ /* dir_count should never be larger than 256 */
+ if (dir_count > 256)
+ goto failed_read;
+
while (dir_count--) {
/*
* Read directory entry.
@@ -183,6 +188,10 @@ static int squashfs_readdir(struct file

size = le16_to_cpu(dire->size) + 1;

+ /* size should never be larger than SQUASHFS_NAME_LEN */
+ if (size > SQUASHFS_NAME_LEN)
+ goto failed_read;
+
err = squashfs_read_metadata(inode->i_sb, dire->name,
&block, &offset, size);
if (err < 0)
--- a/fs/squashfs/namei.c
+++ b/fs/squashfs/namei.c
@@ -176,6 +176,11 @@ static struct dentry *squashfs_lookup(st
length += sizeof(dirh);

dir_count = le32_to_cpu(dirh.count) + 1;
+
+ /* dir_count should never be larger than 256 */
+ if (dir_count > 256)
+ goto data_error;
+
while (dir_count--) {
/*
* Read directory entry.
@@ -187,6 +192,10 @@ static struct dentry *squashfs_lookup(st

size = le16_to_cpu(dire->size) + 1;

+ /* size should never be larger than SQUASHFS_NAME_LEN */
+ if (size > SQUASHFS_NAME_LEN)
+ goto data_error;
+
err = squashfs_read_metadata(dir->i_sb, dire->name,
&block, &offset, size);
if (err < 0)
@@ -228,6 +237,9 @@ exit_lookup:
d_add(dentry, inode);
return ERR_PTR(0);

+data_error:
+ err = -EIO;
+
read_failure:
ERROR("Unable to read directory block [%llx:%x]\n",
squashfs_i(dir)->start + msblk->directory_table,



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