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[PATCH] corrupted cramfs filesystems cause kernel oops

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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>
This commit is contained in:
Phillip Lougher 2006-12-06 20:37:20 -08:00 committed by Linus Torvalds
parent 2e591bbc0d
commit 8bb0269160
1 changed files with 2 additions and 0 deletions
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fs/cramfs/inode.c
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@ -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,