From: Eric Sandeen <sandeen@redhat.com>
Subject: [PATCH RHEL5] CVE-2006-6054 ext2_check_page denial of service
Date: Wed, 03 Jan 2007 15:14:04 -0600
Bugzilla: 217018
Message-Id: <459C1C9C.4000203@redhat.com>
Changelog: fs: ext2_check_page denial of service


for: Bugzilla Bug 217018: CVE-2006-6054 ext2_check_page denial of service

This is in -mm as of 12/27/2006 as 
ext2-skip-pages-past-number-of-blocks-in-ext2_find_entry.patch

This one was pointed out on the MOKB site:
http://kernelfun.blogspot.com/2006/11/mokb-09-11-2006-linux-26x-ext2checkpage.html

If a directory's i_size is corrupted, ext2_find_entry() will keep processing
pages until the i_size is reached, even if there are no more blocks associated
with the directory inode.  This patch puts in some minimal sanity-checking
so that we don't keep checking pages (and issuing errors) if we know there
can be no more data to read, based on the block count of the directory inode.

This is somewhat similar in approach to the ext3 patch I sent earlier this
year.

Thanks,

-Eric

Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Index: linux-2.6.18-1.2910.el5/fs/ext2/dir.c
===================================================================
--- linux-2.6.18-1.2910.el5.orig/fs/ext2/dir.c
+++ linux-2.6.18-1.2910.el5/fs/ext2/dir.c
@@ -368,6 +368,14 @@ struct ext2_dir_entry_2 * ext2_find_entr
 		}
 		if (++n >= npages)
 			n = 0;
+		/* next page is past the blocks we've got */
+		if (unlikely(n > (dir->i_blocks >> (PAGE_CACHE_SHIFT - 9)))) {
+			ext2_error(dir->i_sb, __FUNCTION__,
+				"dir %lu size %lld exceeds block count %llu",
+				dir->i_ino, dir->i_size,
+				(unsigned long long)dir->i_blocks);
+			goto out;
+		}
 	} while (n != start);
 out:
 	return NULL;