linux-kernel - Re: [PATCH] printk: Convert a use of sprintf to snprintf in console

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Message-ID: <20200131070237.GB240941@google.com>
Date:   Fri, 31 Jan 2020 16:02:37 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] printk: Convert a use of sprintf to snprintf in
 console_unlock

On (20/01/30 15:16), Nathan Chancellor wrote:
> When CONFIG_PRINTK is disabled (e.g. when building allnoconfig), clang
> warns:
> 
> ../kernel/printk/printk.c:2416:10: warning: 'sprintf' will always
> overflow; destination buffer has size 0, but format string expands to at
> least 33 [-Wfortify-source]
>                         len = sprintf(text,
>                               ^
> 1 warning generated.
> 
> It is not wrong; text has a zero size when CONFIG_PRINTK is disabled
> because LOG_LINE_MAX and PREFIX_MAX are both zero. Change to snprintf so
> that this case is explicitly handled without any risk of overflow.

We probably can add a note here that for !CONFIG_PRINTK builds
logbuf overflow is very unlikely.

Otherwise,
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

	-ss