linux-ext4 - Re: [PATCH 3/3] ext2: Strengthen xattr block checks

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Date:   Thu, 16 May 2019 09:16:06 +0800
From:   "cgxu519@...o.com.cn" <cgxu519@...o.com.cn>
To:     Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 3/3] ext2: Strengthen xattr block checks

On Wed, 2019-05-15 at 16:01 +0200, Jan Kara wrote:
> Check every entry in xattr block for validity in ext2_xattr_set() to
> detect on disk corruption early. Also since e_value_block field in xattr
> entry is never != 0 in a valid filesystem, just remove checks for it
> once we have established entries are valid.
> 
> Signed-off-by: Jan Kara <jack@...e.cz>

Could we do the entry check in the loop of get/list operation too?

Thanks,
Chengguang

> ---
>  fs/ext2/xattr.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
> index 26a049ca89fb..04a4148d04b3 100644
> --- a/fs/ext2/xattr.c
> +++ b/fs/ext2/xattr.c
> @@ -442,7 +442,9 @@ ext2_xattr_set(struct inode *inode, int name_index, const
> char *name,
>  			struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
>  			if ((char *)next >= end)
>  				goto bad_block;
> -			if (!last->e_value_block && last->e_value_size) {
> +			if (!ext2_xattr_entry_valid(last, sb->s_blocksize))
> +				goto bad_block;
> +			if (last->e_value_size) {
>  				size_t offs = le16_to_cpu(last->e_value_offs);
>  				if (offs < min_offs)
>  					min_offs = offs;
> @@ -482,12 +484,7 @@ ext2_xattr_set(struct inode *inode, int name_index, const
> char *name,
>  		error = -EEXIST;
>  		if (flags & XATTR_CREATE)
>  			goto cleanup;
> -		if (!here->e_value_block && here->e_value_size) {
> -			if (!ext2_xattr_entry_valid(here, sb->s_blocksize))
> -				goto bad_block;
> -			free += EXT2_XATTR_SIZE(
> -					le32_to_cpu(here->e_value_size));
> -		}
> +		free += EXT2_XATTR_SIZE(le32_to_cpu(here->e_value_size));
>  		free += EXT2_XATTR_LEN(name_len);
>  	}
>  	error = -ENOSPC;
> @@ -552,7 +549,7 @@ ext2_xattr_set(struct inode *inode, int name_index, const
> char *name,
>  		here->e_name_len = name_len;
>  		memcpy(here->e_name, name, name_len);
>  	} else {
> -		if (!here->e_value_block && here->e_value_size) {
> +		if (here->e_value_size) {
>  			char *first_val = (char *)header + min_offs;
>  			size_t offs = le16_to_cpu(here->e_value_offs);
>  			char *val = (char *)header + offs;
> @@ -579,7 +576,7 @@ ext2_xattr_set(struct inode *inode, int name_index, const
> char *name,
>  			last = ENTRY(header+1);
>  			while (!IS_LAST_ENTRY(last)) {
>  				size_t o = le16_to_cpu(last->e_value_offs);
> -				if (!last->e_value_block && o < offs)
> +				if (o < offs)
>  					last->e_value_offs =
>  						cpu_to_le16(o + size);
>  				last = EXT2_XATTR_NEXT(last);