linux-kernel - Re: [PATCH v1 10/10] efivars: use generic UUID library

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Message-ID: <20160218150727.GK2651@codeblueprint.co.uk>
Date:	Thu, 18 Feb 2016 15:07:27 +0000
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Theodore Ts'o <tytso@....edu>, Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Lv Zheng <lv.zheng@...el.com>, Mark Brown <broonie@...nel.org>,
	Zhang Rui <rui.zhang@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linux-efi@...r.kernel.org,
	linux-api@...r.kernel.org, linux-nvdimm@...ts.01.org
Subject: Re: [PATCH v1 10/10] efivars: use generic UUID library

On Wed, 17 Feb, at 02:17:28PM, Andy Shevchenko wrote:
> Instead of opencoding let's use generic UUID library functions here.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  fs/efivarfs/inode.c | 40 +++-------------------------------------
>  1 file changed, 3 insertions(+), 37 deletions(-)
> 
> diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c
> index 3381b9d..b579e3a 100644
> --- a/fs/efivarfs/inode.c
> +++ b/fs/efivarfs/inode.c
> @@ -11,6 +11,7 @@
>  #include <linux/fs.h>
>  #include <linux/ctype.h>
>  #include <linux/slab.h>
> +#include <linux/uuid.h>
>  
>  #include "internal.h"
>  
> @@ -44,11 +45,7 @@ struct inode *efivarfs_get_inode(struct super_block *sb,
>   */
>  bool efivarfs_valid_name(const char *str, int len)
>  {
> -	static const char dashes[EFI_VARIABLE_GUID_LEN] = {
> -		[8] = 1, [13] = 1, [18] = 1, [23] = 1
> -	};
>  	const char *s = str + len - EFI_VARIABLE_GUID_LEN;
> -	int i;
>  
>  	/*
>  	 * We need a GUID, plus at least one letter for the variable name,
> @@ -66,37 +63,7 @@ bool efivarfs_valid_name(const char *str, int len)
>  	 *
>  	 *	12345678-1234-1234-1234-123456789abc
>  	 */
> -	for (i = 0; i < EFI_VARIABLE_GUID_LEN; i++) {
> -		if (dashes[i]) {
> -			if (*s++ != '-')
> -				return false;
> -		} else {
> -			if (!isxdigit(*s++))
> -				return false;
> -		}
> -	}
> -
> -	return true;
> -}
> -
> -static void efivarfs_hex_to_guid(const char *str, efi_guid_t *guid)
> -{
> -	guid->b[0] = hex_to_bin(str[6]) << 4 | hex_to_bin(str[7]);
> -	guid->b[1] = hex_to_bin(str[4]) << 4 | hex_to_bin(str[5]);
> -	guid->b[2] = hex_to_bin(str[2]) << 4 | hex_to_bin(str[3]);
> -	guid->b[3] = hex_to_bin(str[0]) << 4 | hex_to_bin(str[1]);
> -	guid->b[4] = hex_to_bin(str[11]) << 4 | hex_to_bin(str[12]);
> -	guid->b[5] = hex_to_bin(str[9]) << 4 | hex_to_bin(str[10]);
> -	guid->b[6] = hex_to_bin(str[16]) << 4 | hex_to_bin(str[17]);
> -	guid->b[7] = hex_to_bin(str[14]) << 4 | hex_to_bin(str[15]);
> -	guid->b[8] = hex_to_bin(str[19]) << 4 | hex_to_bin(str[20]);
> -	guid->b[9] = hex_to_bin(str[21]) << 4 | hex_to_bin(str[22]);
> -	guid->b[10] = hex_to_bin(str[24]) << 4 | hex_to_bin(str[25]);
> -	guid->b[11] = hex_to_bin(str[26]) << 4 | hex_to_bin(str[27]);
> -	guid->b[12] = hex_to_bin(str[28]) << 4 | hex_to_bin(str[29]);
> -	guid->b[13] = hex_to_bin(str[30]) << 4 | hex_to_bin(str[31]);
> -	guid->b[14] = hex_to_bin(str[32]) << 4 | hex_to_bin(str[33]);
> -	guid->b[15] = hex_to_bin(str[34]) << 4 | hex_to_bin(str[35]);
> +	return uuid_is_valid(s);
>  }

I think you've confused yourself here. You've inverted the return
value meaning for efivarfs_valid_name().

Normally I would expect this change to be correct but uuid_is_valid()
returns 0 for success, -EINVAL for failure. Either the function is
misnamed or the return value semantics are wrong.