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authorEric Sandeen <sandeen@redhat.com>2006-12-06 20:36:28 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-07 08:39:33 -0800
commite6c4021190c828d7fa24a464db589f86c6708341 (patch)
tree242161ac94ddf2bff98bb105f8ba804a3b1873e8 /fs/ext4/namei.c
parent40b851348fe9bf49c26025b34261d25142269b60 (diff)
downloadlinux-linaro-e6c4021190c828d7fa24a464db589f86c6708341.tar.gz
[PATCH] handle ext4 directory corruption better
I've been using Steve Grubb's purely evil "fsfuzzer" tool, at http://people.redhat.com/sgrubb/files/fsfuzzer-0.4.tar.gz Basically it makes a filesystem, splats some random bits over it, then tries to mount it and do some simple filesystem actions. At best, the filesystem catches the corruption gracefully. At worst, things spin out of control. As you might guess, we found a couple places in ext4 where things spin out of control :) First, we had a corrupted directory that was never checked for consistency... it was corrupt, and pointed to another bad "entry" of length 0. The for() loop looped forever, since the length of ext4_next_entry(de) was 0, and we kept looking at the same pointer over and over and over and over... I modeled this check and subsequent action on what is done for other directory types in ext4_readdir... (adding this check adds some computational expense; I am testing a followup patch to reduce the number of times we check and re-check these directory entries, in all cases. Thanks for the idea, Andreas). Next we had a root directory inode which had a corrupted size, claimed to be > 200M on a 4M filesystem. There was only really 1 block in the directory, but because the size was so large, readdir kept coming back for more, spewing thousands of printk's along the way. Per Andreas' suggestion, if we're in this read error condition and we're trying to read an offset which is greater than i_blocks worth of bytes, stop trying, and break out of the loop. With these two changes fsfuzz test survives quite well on ext4. Signed-off-by: Eric Sandeen <sandeen@redhat.com> Cc: <linux-ext4@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/ext4/namei.c')
-rw-r--r--fs/ext4/namei.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 8b1bd03d20f..859990eac50 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -552,6 +552,15 @@ static int htree_dirblock_to_tree(struct file *dir_file,
dir->i_sb->s_blocksize -
EXT4_DIR_REC_LEN(0));
for (; de < top; de = ext4_next_entry(de)) {
+ if (!ext4_check_dir_entry("htree_dirblock_to_tree", dir, de, bh,
+ (block<<EXT4_BLOCK_SIZE_BITS(dir->i_sb))
+ +((char *)de - bh->b_data))) {
+ /* On error, skip the f_pos to the next block. */
+ dir_file->f_pos = (dir_file->f_pos |
+ (dir->i_sb->s_blocksize - 1)) + 1;
+ brelse (bh);
+ return count;
+ }
ext4fs_dirhash(de->name, de->name_len, hinfo);
if ((hinfo->hash < start_hash) ||
((hinfo->hash == start_hash) &&