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authorEric Sandeen <sandeen@redhat.com>2006-12-06 23:36:28 -0500
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-07 11:39:33 -0500
commite6c4021190c828d7fa24a464db589f86c6708341 (patch)
tree242161ac94ddf2bff98bb105f8ba804a3b1873e8
parent40b851348fe9bf49c26025b34261d25142269b60 (diff)
[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>
-rw-r--r--fs/ext4/dir.c3
-rw-r--r--fs/ext4/namei.c9
2 files changed, 12 insertions, 0 deletions
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index f8595787a70e..f2ed3e7fb9f5 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -153,6 +153,9 @@ static int ext4_readdir(struct file * filp,
153 ext4_error (sb, "ext4_readdir", 153 ext4_error (sb, "ext4_readdir",
154 "directory #%lu contains a hole at offset %lu", 154 "directory #%lu contains a hole at offset %lu",
155 inode->i_ino, (unsigned long)filp->f_pos); 155 inode->i_ino, (unsigned long)filp->f_pos);
156 /* corrupt size? Maybe no more blocks to read */
157 if (filp->f_pos > inode->i_blocks << 9)
158 break;
156 filp->f_pos += sb->s_blocksize - offset; 159 filp->f_pos += sb->s_blocksize - offset;
157 continue; 160 continue;
158 } 161 }
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 8b1bd03d20f5..859990eac504 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,
552 dir->i_sb->s_blocksize - 552 dir->i_sb->s_blocksize -
553 EXT4_DIR_REC_LEN(0)); 553 EXT4_DIR_REC_LEN(0));
554 for (; de < top; de = ext4_next_entry(de)) { 554 for (; de < top; de = ext4_next_entry(de)) {
555 if (!ext4_check_dir_entry("htree_dirblock_to_tree", dir, de, bh,
556 (block<<EXT4_BLOCK_SIZE_BITS(dir->i_sb))
557 +((char *)de - bh->b_data))) {
558 /* On error, skip the f_pos to the next block. */
559 dir_file->f_pos = (dir_file->f_pos |
560 (dir->i_sb->s_blocksize - 1)) + 1;
561 brelse (bh);
562 return count;
563 }
555 ext4fs_dirhash(de->name, de->name_len, hinfo); 564 ext4fs_dirhash(de->name, de->name_len, hinfo);
556 if ((hinfo->hash < start_hash) || 565 if ((hinfo->hash < start_hash) ||
557 ((hinfo->hash == start_hash) && 566 ((hinfo->hash == start_hash) &&