linux-kernel - Re: [此邮件可能存在风险] [PATCH v2 7/9] lib/vsprintf: Replace space with '

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Message-ID: <1519095438.2772.13.camel@hxt-semitech.com>
Date:   Tue, 20 Feb 2018 02:57:19 +0000
From:   "Yang, Shunyong" <shunyong.yang@...-semitech.com>
To:     "joe@...ches.com" <joe@...ches.com>,
        "linux@...musvillemoes.dk" <linux@...musvillemoes.dk>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "me@...in.cc" <me@...in.cc>, "pmladek@...e.com" <pmladek@...e.com>
CC:     "Zheng, Joey" <yu.zheng@...-semitech.com>
Subject: Re: [此邮件可能存在风险]  [PATCH v2 7/9] lib/vsprintf: Replace space with '_' before crng is ready

Hi, Andy,

Many thanks for the change. I am on Chinese New Year travel and slow
response. :-)

Thanks.
Shunyong.

On Fri, 2018-02-16 at 23:07 +0200, Andy Shevchenko wrote:
> From: Shunyong Yang <shunyong.yang@...-semitech.com>
> 
> Before crng is ready, output of "%p" composes of "(ptrval)" and
> left padding spaces for alignment as no random address can be
> generated. This seems a little strange when default string width
> is larger than strlen("(ptrval)").
> 
> For example, when irq domain names are built with "%p", the nodes
> under /sys/kernel/debug/irq/domains like this on AArch64 system,
> 
> [root@y irq]# ls domains/
> default                   irqchip@        (ptrval)-2
> irqchip@        (ptrval)-4  \_SB_.TCS0.QIC1  \_SB_.TCS0.QIC3
> irqchip@        (ptrval)  irqchip@        (ptrval)-3
> \_SB_.TCS0.QIC0             \_SB_.TCS0.QIC2
> 
> The name "irqchip@        (ptrval)-2" is not so readable in console
> output.
> 
> This patch replaces space with readable "_" when output needs
> padding.
> Following is the output after applying the patch,
> 
> [root@y domains]# ls
> default                   irqchip@(____ptrval____)-2
> irqchip@(____ptrval____)-4  \_SB_.TCS0.QIC1  \_SB_.TCS0.QIC3
> irqchip@(____ptrval____)  irqchip@(____ptrval____)-3  \_SB_.TCS0.QIC0
> \_SB_.TCS0.QIC2
> 
> There is same problem in some subsystem's dmesg output. Moreover,
> someone may call "%p" in a similar case. In addition, the timing of
> crng initialization done may vary on different system. So, the change
> is made in vsprintf.c.
> 
> Cc: Joey Zheng <yu.zheng@...-semitech.com>
> Suggested-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> Signed-off-by: Shunyong Yang <shunyong.yang@...-semitech.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  lib/vsprintf.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 9004bbb3d84d..97be2d07297a 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1681,12 +1681,13 @@ early_initcall(initialize_ptr_random);
>  /* Maps a pointer to a 32 bit unique identifier. */
>  static char *ptr_to_id(char *buf, char *end, void *ptr, struct
> printf_spec spec)
>  {
> +	const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" :
> "(ptrval)";
>  	unsigned long hashval;
>  
>  	if (unlikely(!have_filled_random_ptr_key)) {
>  		spec.field_width = 2 * sizeof(ptr);
>  		/* string length must be less than default_width */
> -		return string(buf, end, "(ptrval)", spec);
> +		return string(buf, end, str, spec);
>  	}
>  
>  #ifdef CONFIG_64BIT