Squashfs: handle corruption of directory structure
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>
diff --git a/fs/squashfs/dir.c b/fs/squashfs/dir.c
index 0dc340a..3f79cd1 100644
--- a/fs/squashfs/dir.c
+++ b/fs/squashfs/dir.c
@@ -172,6 +172,11 @@
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 @@
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)