From: Eric Sandeen <esandeen@redhat.com>
Subject: [PATCH RHEL5] fix zlib_inflate oops due to corrupted cramfs image
Date: Thu, 9 Nov 2006 11:26:07 -0600
Bugzilla: 214705
Message-Id: <200611091726.kA9HQ74f005094@neon.msp.redhat.com>
Changelog: cramfs: fix zlib_inflate oops with corrupted image


For BZ: 214705: [RHEL5] corrupted cramfs crashes in zlib_inflate

This patch is upstream in the -mm tree.

-----


Steve Grubb's fzfuzzer tool (http://people.redhat.com/sgrubb/files/
fsfuzzer-0.6.tar.gz) generates corrupt Cramfs filesystems which cause
Cramfs to kernel oops in cramfs_uncompress_block().  The cause of the oops
is an unchecked corrupted block length field read by cramfs_readpage().

This patch adds a sanity check to cramfs_readpage() which checks that the
block length field is sensible.  The (PAGE_CACHE_SIZE << 1) size check is
intentional, even though the uncompressed data is not going to be larger
than PAGE_CACHE_SIZE, gzip sometimes generates compressed data larger than
the original source data.  Mkcramfs checks that the compressed size is
always less than or equal to PAGE_CACHE_SIZE << 1.  Of course Cramfs could
use the original uncompressed data in this case, but it doesn't.

Signed-off-by: Phillip Lougher <phillip@lougher.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 fs/cramfs/inode.c |    2 ++
 1 files changed, 2 insertions(+)

Index: linux-2.6.18-1.2732.el5/fs/cramfs/inode.c
===================================================================
--- linux-2.6.18-1.2732.el5.orig/fs/cramfs/inode.c
+++ linux-2.6.18-1.2732.el5/fs/cramfs/inode.c
@@ -482,6 +482,8 @@ static int cramfs_readpage(struct file *
 		pgdata = kmap(page);
 		if (compr_len == 0)
 			; /* hole */
+		else if (compr_len > (PAGE_CACHE_SIZE << 1))
+			printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
 		else {
 			mutex_lock(&read_mutex);
 			bytes_filled = cramfs_uncompress_block(pgdata,