From: Phillip Lougher <phillip@lougher.org.uk>
Date: Thu, 7 Dec 2006 04:37:20 +0000 (-0800)
Subject: [PATCH] corrupted cramfs filesystems cause kernel oops
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=8bb0269160df2a60764013994d0bc5165406cf4a;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git

[PATCH] corrupted cramfs filesystems cause kernel oops

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>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index a624c3ec8189..0509cedd415c 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -481,6 +481,8 @@ static int cramfs_readpage(struct file *file, struct page * page)
 		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,