Re: Fwd: [PATCH net-next 1/2] lib: string: add strreplace_nonalnum

Greg Kroah-Hartman
2019-03-03T17:56:10Z

On Sun, Mar 03, 2019 at 06:47:32PM +0100, Heiner Kallweit wrote:
> I submitted this through the netdev tree, maybe relevant for you as well.
> See also here: https://marc.info/?t=155103900100003&r=1&w=2
>
> -------- Forwarded Message --------
> Subject: [PATCH net-next 1/2] lib: string: add strreplace_nonalnum
> Date: Sun, 3 Mar 2019 18:20:50 +0100
> From: Heiner Kallweit <hkallweit1@gmail.com>
> To: Florian Fainelli <f.fainelli@gmail.com>, Andrew Lunn <andrew@lunn.ch>, David Miller <davem@davemloft.net>
> CC: netdev@vger.kernel.org <netdev@vger.kernel.org>
>
> Add a new function strreplace_nonalnum that replaces all
> non-alphanumeric characters. Such functionality is needed e.g. when a
> string is supposed to be used in a sysfs file name. If '\0' is given
> as new character then non-alphanumeric characters are cut.

sysfs doesn't have any such requirements, it can use whatever you want
to give it for a filename.

So don't create a random kernel function for sysfs please.

>
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
> include/linux/string.h | 1 +
> lib/string.c | 27 +++++++++++++++++++++++++++
> 2 files changed, 28 insertions(+)
>
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 7927b875f..d827b0b0f 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -169,6 +169,7 @@ static inline void memcpy_flushcache(void *dst, const void *src, size_t cnt)
> #endif
> void *memchr_inv(const void *s, int c, size_t n);
> char *strreplace(char *s, char old, char new);
> +char *strreplace_nonalnum(char *s, char new);
>
> extern void kfree_const(const void *x);
>
> diff --git a/lib/string.c b/lib/string.c
> index 38e4ca08e..f2b1baf96 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -1047,6 +1047,33 @@ char *strreplace(char *s, char old, char new)
> }
> EXPORT_SYMBOL(strreplace);
>
> +/**
> + * strreplace_nonalnum - Replace all non-alphanumeric characters in a string.
> + * @s: The string to operate on.
> + * @new: The character non-alphanumeric characters are replaced with.
> + *
> + * If new is '\0' then non-alphanumeric characters are cut.
> + *
> + * Returns pointer to the nul byte at the end of the modified string.

Why do you need to point to the end of the string?

> + */
> +char *strreplace_nonalnum(char *s, char new)
> +{
> + char *p = s;
> +
> + for (; *s; ++s)
> + if (isalnum(*s)) {
> + if (p != s)
> + *p = *s;
> + ++p;
> + } else if (new) {
> + *p++ = new;
> + }
> + *p = '\0';

No max length? No error checking? Surely we can do better, see the
long thread on the kernel-hardnening list about string functions please.

greg k-h