linux-ext4 - Re: [PATCH] ext4: check inline directory before converting

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Message-Id: <253FEEC3-F619-4D9B-8358-A8FC8A832740@dilger.ca>
Date:	Thu, 24 Jul 2014 16:41:04 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
Cc:	Theodore Ts'o <tytso@....edu>, Zheng Liu <gnehzuil.liu@...il.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: check inline directory before converting

On Jul 24, 2014, at 3:22 PM, Darrick J. Wong <darrick.wong@...cle.com> wrote:
> Before converting an inline directory to a regular directory, check
> the directory entries to make sure they're not obviously broken.
> This helps us to avoid a BUG_ON if one of the dirents is trashed.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> ---
> fs/ext4/inline.c |   37 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 37 insertions(+)
> 
> diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
> index 645205d..c79d8e7 100644
> --- a/fs/ext4/inline.c
> +++ b/fs/ext4/inline.c
> @@ -1157,6 +1157,31 @@ out:
> 	return err;
> }
> 
> +static int ext4_check_all_de(struct inode *dir, struct buffer_head *bh,
> +			     void *buf, int buf_size)

It would seem that this function would be useful in ext4_readdir(), which
open-codes something very similar?  It might be better to locate this
function in ext4/dir.c since it doesn't appear to have anything specific
to do with inline directories.

Cheers, Andreas

> +{
> +	struct ext4_dir_entry_2 *de;
> +	int nlen, rlen;
> +	unsigned int offset = 0;
> +	char *top;
> +
> +	de = (struct ext4_dir_entry_2 *)buf;
> +	top = buf + buf_size;
> +	while ((char *) de < top) {
> +		if (ext4_check_dir_entry(dir, NULL, de, bh,
> +					 buf, buf_size, offset))
> +			return -EIO;
> +		nlen = EXT4_DIR_REC_LEN(de->name_len);
> +		rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
> +		de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
> +		offset += rlen;
> +	}
> +	if ((char *) de > top)
> +		return -EIO;
> +
> +	return 0;
> +}
> +
> static int ext4_convert_inline_data_nolock(handle_t *handle,
> 					   struct inode *inode,
> 					   struct ext4_iloc *iloc)
> @@ -1178,6 +1203,18 @@ static int ext4_convert_inline_data_nolock(handle_t *handle,
> 	if (error < 0)
> 		goto out;
> 
> +	/*
> +	 * Make sure the inline directory entries pass checks before we try to
> +	 * convert them, so that we avoid touching stuff that needs fsck.
> +	 */
> +	if (S_ISDIR(inode->i_mode)) {
> +		error = ext4_check_all_de(inode, iloc->bh,
> +					buf + EXT4_INLINE_DOTDOT_SIZE,
> +					inline_size - EXT4_INLINE_DOTDOT_SIZE);
> +		if (error)
> +			goto out;
> +	}
> +
> 	error = ext4_destroy_inline_data_nolock(handle, inode);
> 	if (error)
> 		goto out;
> --
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Cheers, Andreas






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