netdev - Re: [PATCH v2 1/4] lib: move strtobool to kstrtobool

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Date:	Fri, 05 Feb 2016 00:55:11 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Kees Cook <keescook@...omium.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Joe Perches <joe@...ches.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Amitkumar Karwar <akarwar@...vell.com>,
	Nishant Sarmukadam <nishants@...vell.com>,
	Kalle Valo <kvalo@...eaurora.org>,
	Steve French <sfrench@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>, x86@...nel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] lib: move strtobool to kstrtobool

On Thu, Feb 04 2016, Kees Cook <keescook@...omium.org> wrote:

> Create the kstrtobool_from_user helper and moves strtobool logic into
> the new kstrtobool (matching all the other kstrto* functions). Provides
> an inline wrapper for existing strtobool callers.
>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  include/linux/kernel.h |  3 +++
>  include/linux/string.h |  6 +++++-
>  lib/kstrtox.c          | 35 +++++++++++++++++++++++++++++++++++
>  lib/string.c           | 29 -----------------------------
>  4 files changed, 43 insertions(+), 30 deletions(-)
>
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index f31638c6e873..cdc25f47a23f 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -357,6 +357,7 @@ int __must_check kstrtou16(const char *s, unsigned int base, u16 *res);
>  int __must_check kstrtos16(const char *s, unsigned int base, s16 *res);
>  int __must_check kstrtou8(const char *s, unsigned int base, u8 *res);
>  int __must_check kstrtos8(const char *s, unsigned int base, s8 *res);
> +int __must_check kstrtobool(const char *s, unsigned int base, bool *res);
>  
>  int __must_check kstrtoull_from_user(const char __user *s, size_t count, unsigned int base, unsigned long long *res);
>  int __must_check kstrtoll_from_user(const char __user *s, size_t count, unsigned int base, long long *res);
> @@ -368,6 +369,8 @@ int __must_check kstrtou16_from_user(const char __user *s, size_t count, unsigne
>  int __must_check kstrtos16_from_user(const char __user *s, size_t count, unsigned int base, s16 *res);
>  int __must_check kstrtou8_from_user(const char __user *s, size_t count, unsigned int base, u8 *res);
>  int __must_check kstrtos8_from_user(const char __user *s, size_t count, unsigned int base, s8 *res);
> +int __must_check kstrtobool_from_user(const char __user *s, size_t count,
> +				      unsigned int base, bool *res);
>  
>  static inline int __must_check kstrtou64_from_user(const char __user *s, size_t count, unsigned int base, u64 *res)
>  {
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 9eebc66d957a..d2fb21b1081d 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -128,7 +128,11 @@ extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
>  extern void argv_free(char **argv);
>  
>  extern bool sysfs_streq(const char *s1, const char *s2);
> -extern int strtobool(const char *s, bool *res);
> +extern int kstrtobool(const char *s, unsigned int base, bool *res);
> +static inline int strtobool(const char *s, bool *res)
> +{
> +	return kstrtobool(s, 0, res);
> +}
>  
>  #ifdef CONFIG_BINARY_PRINTF
>  int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args);
> diff --git a/lib/kstrtox.c b/lib/kstrtox.c
> index 94be244e8441..e18f088704d7 100644
> --- a/lib/kstrtox.c
> +++ b/lib/kstrtox.c
> @@ -321,6 +321,40 @@ int kstrtos8(const char *s, unsigned int base, s8 *res)
>  }
>  EXPORT_SYMBOL(kstrtos8);
>  
> +/**
> + * kstrtobool - convert common user inputs into boolean values
> + * @s: input string
> + * @base: ignored
> + * @res: result
> + *
> + * This routine returns 0 iff the first character is one of 'Yy1Nn0'.
> + * Otherwise it will return -EINVAL.  Value pointed to by res is
> + * updated upon finding a match.
> + */
> +int kstrtobool(const char *s, unsigned int base, bool *res)
> +{

Being able to create the kstrtobool_from_user with a single macro
invocation is convenient, but I don't think that justifies the ugliness
of having an unused parameter. People reading this code or trying to use
the interface will wonder what it's doing there, and it will generate
slightly larger code for all the users of strtobool.

So I'd just make a separate explicit definition of kstrtobool_from_user
(the stack buffer sizing doesn't apply to the strings we want to parse
anyway, though 11 is of course plenty).

Rasmus