Re: [PATCH] x86/mtrr: Remove unnecessary strlen() in mtrr_write()

Ingo Molnar
2025-02-25T13:35:21Z

* Thorsten Blum <thorsten.blum@linux.dev> wrote:

> The local variable length already holds the string length after calling
> strncpy_from_user(). Using another local variable linlen and calling
> strlen() is therefore unnecessary and can be removed. Remove linlen
> and strlen() and use length instead.
>
> Compile-tested only.
>
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
> arch/x86/kernel/cpu/mtrr/if.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mtrr/if.c b/arch/x86/kernel/cpu/mtrr/if.c
> index a5c506f6da7f..4049235b1bfe 100644
> --- a/arch/x86/kernel/cpu/mtrr/if.c
> +++ b/arch/x86/kernel/cpu/mtrr/if.c
> @@ -99,7 +99,6 @@ mtrr_write(struct file *file, const char __user *buf, size_t len, loff_t * ppos)
> char *ptr;
> char line[LINE_SIZE];
> int length;
> - size_t linelen;
>
> memset(line, 0, LINE_SIZE);
>
> @@ -108,9 +107,8 @@ mtrr_write(struct file *file, const char __user *buf, size_t len, loff_t * ppos)
> if (length < 0)
> return length;
>
> - linelen = strlen(line);
> - ptr = line + linelen - 1;
> - if (linelen && *ptr == '\n')
> + ptr = line + length - 1;
> + if (length && *ptr == '\n')
> *ptr = '\0';

I see no corner-case analysis in the changelog about what may happen if
the copy fails partially.

Thanks,

Ingo