linux-kernel - RE: [PATCH v1 1/1] seq_file: Replace strncpy()+nul by strscpy()

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Message-ID: <4aef09112d0c4a59a1a3fa393af59f37@AcuMS.aculab.com>
Date:   Tue, 18 Jul 2023 09:42:13 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Andy Shevchenko' <andriy.shevchenko@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Kees Cook <keescook@...omium.org>
Subject: RE: [PATCH v1 1/1] seq_file: Replace strncpy()+nul by strscpy()

From: Andy Shevchenko
> Sent: 17 July 2023 10:34
...
>  #define seq_show_option_n(m, name, value, length) {	\
>  	char val_buf[length + 1];			\
> -	strncpy(val_buf, value, length);		\
> -	val_buf[length] = '\0';				\
> +	strscpy(val_buf, value, sizeof(val_buf));	\
>  	seq_show_option(m, name, val_buf);		\
>  }

Why the extra double-copy with (potentially) a VLA?

seq_show_option() calls seq_escape_str(),
seq_escape_str calls seq_escape_mem(...  strlen(src) ...).

Implement seq_show_option() as seq_show_option_n(... strlen(value))
and use seq_escape_mem() for the value.

	David

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