Re: [RFC PATCH] mkfs.f2fs: avoid dumplicate extension

[Chao Yu <chao@kernel.org>]

Hi Sheng Yong,

On 11/28/15 12:55 AM, Sheng Yong wrote:
> Before copying user specified extension to extension_list, check if it is
> already in the list.
> 
> Signed-off-by: Sheng Yong <shengyong1@huawei.com>
> ---
>  mkfs/f2fs_format.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/mkfs/f2fs_format.c b/mkfs/f2fs_format.c
> index 176bdea..b7ea19f 100644
> --- a/mkfs/f2fs_format.c
> +++ b/mkfs/f2fs_format.c
> @@ -118,6 +118,26 @@ const char *media_ext_lists[] = {
>  	NULL
>  };
>  
> +static int extension_exist(const char *name, const int len)

bool is_extension_exist?

> +{
> +	const char **extlist = media_ext_lists;
> +	int name_len, min_len;
> +	int ret;
> +
> +
> +	while (*extlist) {
> +		name_len = strlen(*extlist);
> +		min_len = name_len < len ? name_len : len;
> +		ret = strncmp(*extlist, name, min_len);

How about using strcmp(*extlist, name)? It will return 0 only if the two strings
are the same.

> +
> +		if (ret == 0 && name_len == len)
> +			return 1;
> +		extlist++;
> +	}
> +
> +	return 0;
> +}
> +
>  static void configure_extension_list(void)
>  {
>  	const char **extlist = media_ext_lists;
> @@ -144,7 +164,8 @@ static void configure_extension_list(void)
>  	ue = strtok(ext_str, ",");
>  	while (ue != NULL) {
>  		name_len = strlen(ue);

We should verify the length of extension to avoid memcpy overflow. I will send a
patch for fixing.

> -		memcpy(sb.extension_list[i++], ue, name_len);
> +		if (!extension_exist(ue, name_len))

How do you think of comparing extension user defined with sb.extension_list?
In this way, duplication user defined can be avoided completely.

Thanks,

> +			memcpy(sb.extension_list[i++], ue, name_len);
>  		ue = strtok(NULL, ",");
>  		if (i >= F2FS_MAX_EXTENSION)
>  			break;
> 

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