Re: [此邮件可能存在风险] [PATCH v2 7/9] lib/vsprintf: Replace space with '_' before crng is ready

Yang, Shunyong
2018-02-20T02:57:48Z

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@hxt-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@hxt-semitech.com>
> Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Signed-off-by: Shunyong Yang <shunyong.yang@hxt-semitech.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.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