[PATCH] erofs-utils: sort shared xattr

[Gao Xiang]

Hi Jianan,

On Thu, Oct 21, 2021 at 10:58:47AM +0800, Huang Jianan via Linux-erofs wrote:
> Sort shared xattr before writing to disk to ensure the consistency
> of reproducible builds.

How about adding it as an option?

> ---
>  lib/xattr.c | 34 ++++++++++++++++++++++++++++++----
>  1 file changed, 30 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/xattr.c b/lib/xattr.c
> index 196133a..f17e57e 100644
> --- a/lib/xattr.c
> +++ b/lib/xattr.c
> @@ -171,7 +171,7 @@ static struct xattr_item *parse_one_xattr(const char *path, const char *key,
>  	/* allocate key-value buffer */
>  	len[0] = keylen - prefixlen;
>  
> -	kvbuf = malloc(len[0] + len[1]);
> +	kvbuf = malloc(len[0] + len[1] + 1);
>  	if (!kvbuf)
>  		return ERR_PTR(-ENOMEM);
>  	memcpy(kvbuf, key + prefixlen, len[0]);
> @@ -196,6 +196,7 @@ static struct xattr_item *parse_one_xattr(const char *path, const char *key,
>  			len[1] = ret;
>  		}
>  	}
> +	kvbuf[len[0] + len[1]] = '\0';
>  	return get_xattritem(prefix, kvbuf, len);
>  }
>  
> @@ -398,7 +399,7 @@ static int erofs_droid_xattr_set_caps(struct erofs_inode *inode)
>  	len[0] = sizeof("capability") - 1;
>  	len[1] = sizeof(caps);
>  
> -	kvbuf = malloc(len[0] + len[1]);
> +	kvbuf = malloc(len[0] + len[1] + 1);
>  	if (!kvbuf)
>  		return -ENOMEM;
>  
> @@ -409,6 +410,7 @@ static int erofs_droid_xattr_set_caps(struct erofs_inode *inode)
>  	caps.data[1].permitted = (u32) (capabilities >> 32);
>  	caps.data[1].inheritable = 0;
>  	memcpy(kvbuf + len[0], &caps, len[1]);
> +	kvbuf[len[0] + len[1]] = '\0';
>  
>  	item = get_xattritem(EROFS_XATTR_INDEX_SECURITY, kvbuf, len);
>  	if (IS_ERR(item))
> @@ -562,13 +564,23 @@ static struct erofs_bhops erofs_write_shared_xattrs_bhops = {
>  	.flush = erofs_bh_flush_write_shared_xattrs,
>  };
>  
> +static int comp_xattr_item(const void *a, const void *b)
> +{
> +	const struct xattr_item *ia, *ib;
> +
> +	ia = (*((const struct inode_xattr_node **)a))->item;
> +	ib = (*((const struct inode_xattr_node **)b))->item;
> +
> +	return strcmp(ia->kvbuf, ib->kvbuf);

could we use strncmp (len[0] + len[1]) instead?

Thanks,
Gao Xiang