linux-kernel - Re: [PATCH] kcsan: Use min() to fix Coccinelle warning

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Date: Mon, 24 Jun 2024 09:02:47 +0200
From: Marco Elver <elver@...gle.com>
To: Thorsten Blum <thorsten.blum@...lux.com>
Cc: dvyukov@...gle.com, kasan-dev@...glegroups.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kcsan: Use min() to fix Coccinelle warning

On Mon, 24 Jun 2024 at 00:08, Thorsten Blum <thorsten.blum@...lux.com> wrote:
>
> Fixes the following Coccinelle/coccicheck warning reported by
> minmax.cocci:
>
>         WARNING opportunity for min()
>
> Use size_t instead of int for the result of min().
>
> Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>

Reviewed-by: Marco Elver <elver@...gle.com>

Thanks for polishing (but see below). Please compile-test with
CONFIG_KCSAN=y if you haven't.

> ---
>  kernel/kcsan/debugfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/kcsan/debugfs.c b/kernel/kcsan/debugfs.c
> index 1d1d1b0e4248..11b891fe6f7a 100644
> --- a/kernel/kcsan/debugfs.c
> +++ b/kernel/kcsan/debugfs.c
> @@ -225,7 +225,7 @@ debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *o
>  {
>         char kbuf[KSYM_NAME_LEN];
>         char *arg;
> -       int read_len = count < (sizeof(kbuf) - 1) ? count : (sizeof(kbuf) - 1);
> +       size_t read_len = min(count, (sizeof(kbuf) - 1));

While we're here polishing things this could be:

const size_t read_len = min(count, sizeof(kbuf) - 1);

( +const, remove redundant () )

>         if (copy_from_user(kbuf, buf, read_len))
>                 return -EFAULT;
> --
> 2.45.2