linux-kernel - RE: [PATCH 1/2] exfat: add dir-entry set checksum validation

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Date:   Mon, 10 Aug 2020 15:19:15 +0900
From:   "Namjae Jeon" <namjae.jeon@...sung.com>
To:     "'Tetsuhiro Kohada'" <kohada.t2@...il.com>
Cc:     <kohada.tetsuhiro@...mitsubishielectric.co.jp>,
        <mori.takahiro@...mitsubishielectric.co.jp>,
        <motai.hirotaka@...mitsubishielectric.co.jp>,
        "'Sungjong Seo'" <sj1557.seo@...sung.com>,
        <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] exfat: add dir-entry set checksum validation

> Add checksum validation for dir-entry set when getting it.
> exfat_calc_dir_chksum_with_entry_set() also validates entry-type.
> 
> ** This patch depends on:
>   '[PATCH v3] exfat: integrates dir-entry getting and validation'
> 
> Signed-off-by: Tetsuhiro Kohada <kohada.t2@...il.com>
> ---
>  fs/exfat/dir.c | 34 ++++++++++++++++++++++------------
>  1 file changed, 22 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c index c9715c7a55a1..2e79ac464f5f 100644
> --- a/fs/exfat/dir.c
> +++ b/fs/exfat/dir.c
> @@ -563,18 +563,27 @@ int exfat_remove_entries(struct inode *inode, struct exfat_chain *p_dir,
>  	return 0;
>  }
> 
> -void exfat_update_dir_chksum_with_entry_set(struct exfat_entry_set_cache *es)
> +static int exfat_calc_dir_chksum_with_entry_set(struct
> +exfat_entry_set_cache *es, u16 *chksum)
>  {
> -	int chksum_type = CS_DIR_ENTRY, i;
> -	unsigned short chksum = 0;
>  	struct exfat_dentry *ep;
> +	int i;
> 
> -	for (i = 0; i < es->num_entries; i++) {
> -		ep = exfat_get_validated_dentry(es, i, TYPE_ALL);
> -		chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, chksum,
> -					     chksum_type);
> -		chksum_type = CS_DEFAULT;
> +	ep = container_of(es->de_file, struct exfat_dentry, dentry.file);
> +	*chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, 0, CS_DIR_ENTRY);
> +	for (i = 0; i < es->de_file->num_ext; i++) {
> +		ep = exfat_get_validated_dentry(es, 1 + i, TYPE_SECONDARY);
> +		if (!ep)
> +			return -EIO;
> +		*chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, *chksum, CS_DEFAULT);
>  	}
> +	return 0;
We can return checksum after removing u16 *chksum argument.
> +}
> +
> +void exfat_update_dir_chksum_with_entry_set(struct
> +exfat_entry_set_cache *es) {
> +	u16 chksum;
> +
> +	exfat_calc_dir_chksum_with_entry_set(es, &chksum);
>  	es->de_file->checksum = cpu_to_le16(chksum);
>  	es->modified = true;
>  }
> @@ -775,6 +784,7 @@ struct exfat_entry_set_cache *exfat_get_dentry_set(struct super_block *sb,
>  	struct exfat_entry_set_cache *es;
>  	struct exfat_dentry *ep;
>  	struct buffer_head *bh;
> +	u16 chksum;
> 
>  	if (p_dir->dir == DIR_DELETED) {
>  		exfat_err(sb, "access to deleted dentry"); @@ -839,10 +849,10 @@ struct
> exfat_entry_set_cache *exfat_get_dentry_set(struct super_block *sb,
>  		goto free_es;
>  	es->de_stream = &ep->dentry.stream;
> 
> -	for (i = 2; i < es->num_entries; i++) {
> -		if (!exfat_get_validated_dentry(es, i, TYPE_SECONDARY))
> -			goto free_es;
> -	}
> +	if (max_entries == ES_ALL_ENTRIES &&
> +	    ((exfat_calc_dir_chksum_with_entry_set(es, &chksum) ||
> +	      chksum != le16_to_cpu(es->de_file->checksum))))
Please add error print log if checksum mismatch error happen.
> +		goto free_es;
> 
>  	return es;
> 
> --
> 2.25.1