linux-kernel - [58/71] Squashfs: handle corruption of directory structure

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Date:	Wed, 13 Apr 2011 09:10:21 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Phillip Lougher <phillip@...gher.demon.co.uk>
Subject: [58/71] Squashfs: handle corruption of directory structure

2.6.33-longterm review patch.  If anyone has any objections, please let us know.

------------------

From: Phillip Lougher <phillip@...gher.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@...gher.demon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.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
@@ -173,6 +173,11 @@ 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.
@@ -184,6 +189,10 @@ 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
@@ -175,6 +175,11 @@ 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.
@@ -186,6 +191,10 @@ 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)
@@ -227,6 +236,9 @@ 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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