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Commit 8bb02691 authored by Phillip Lougher's avatar Phillip Lougher Committed by Linus Torvalds
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[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: default avatarPhillip Lougher <phillip@lougher.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 2e591bbc

fs/cramfs/inode.c

+2 −0
Original line number Diff line number Diff line
@@ -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,