From: Baokun Li <libaokun1@xxxxxxxxxx>
commit f9ca51596bbfd0f9c386dd1c613c394c78d9e5e6 upstream.
The syzbot constructs a directory that has no dirblock but is non-inline,
i.e. the first directory block is a hole. And no errors are reported when
creating files in this directory in the following flow.
ext4_mknod
...
ext4_add_entry
// Read block 0
ext4_read_dirblock(dir, block, DIRENT)
bh = ext4_bread(NULL, inode, block, 0)
if (!bh && (type == INDEX || type == DIRENT_HTREE))
// The first directory block is a hole
// But type == DIRENT, so no error is reported.
After that, we get a directory block without '.' and '..' but with a valid
dentry. This may cause some code that relies on dot or dotdot (such as
make_indexed_dir()) to crash.
Therefore when ext4_read_dirblock() finds that the first directory block
is a hole report that the filesystem is corrupted and return an error to
avoid loading corrupted data from disk causing something bad.
Reported-by: syzbot+ae688d469e36fb5138d0@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=ae688d469e36fb5138d0
Fixes: 4e19d6b65fb4 ("ext4: allow directory holes")
Cc: stable@xxxxxxxxxx
Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Link: https://patch.msgid.link/20240702132349.2600605-3-libaokun@xxxxxxxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/namei.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -134,10 +134,11 @@ static struct buffer_head *__ext4_read_d
return bh;
}
- if (!bh && (type == INDEX || type == DIRENT_HTREE)) {
+ /* The first directory block must not be a hole. */
+ if (!bh && (type == INDEX || type == DIRENT_HTREE || block == 0)) {
ext4_error_inode(inode, func, line, block,
- "Directory hole found for htree %s block",
- (type == INDEX) ? "index" : "leaf");
+ "Directory hole found for htree %s block %u",
+ (type == INDEX) ? "index" : "leaf", block);
return ERR_PTR(-EFSCORRUPTED);
}
if (!bh)
@@ -2850,10 +2851,7 @@ bool ext4_empty_dir(struct inode *inode)
EXT4_ERROR_INODE(inode, "invalid size");
return true;
}
- /* The first directory block must not be a hole,
- * so treat it as DIRENT_HTREE
- */
- bh = ext4_read_dirblock(inode, 0, DIRENT_HTREE);
+ bh = ext4_read_dirblock(inode, 0, EITHER);
if (IS_ERR(bh))
return true;
@@ -3425,10 +3423,7 @@ static struct buffer_head *ext4_get_firs
struct ext4_dir_entry_2 *de;
unsigned int offset;
- /* The first directory block must not be a hole, so
- * treat it as DIRENT_HTREE
- */
- bh = ext4_read_dirblock(inode, 0, DIRENT_HTREE);
+ bh = ext4_read_dirblock(inode, 0, EITHER);
if (IS_ERR(bh)) {
*retval = PTR_ERR(bh);
return NULL;
Patches currently in stable-queue which might be from libaokun1@xxxxxxxxxx are
queue-4.19/ext4-make-sure-the-first-directory-block-is-not-a-hole.patch
queue-4.19/ext4-check-dot-and-dotdot-of-dx_root-before-making-dir-indexed.patch
