[patch] patch

1910_cramfs-block-corruption.patch (text/plain), 1.67 KB, created by Daniel Drake (RETIRED) on 2006-12-23 08:33:41 UTC

From: Phillip Lougher <[e-mail]>
Date: Thu, 7 Dec 2006 04:37:20 +0000 (-0800)
Subject: [PATCH] corrupted cramfs filesystems cause kernel oops
X-Git-Tag: v2.6.20-rc1
X-Git-Url: http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=8bb0269160df2a60764013994d0bc5165406cf4a

[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 <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>
---

--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -481,6 +481,8 @@ 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,