linux-kernel - Re: [PATCH v4 4/4] pr_emerg add WARN

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 1 Feb 2016 20:58:10 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jeffrey Merkey <jeffmerkey@...il.com>
Cc:	linux-kernel@...r.kernel.org, Jason@...c4.com, aconole@...hat.com,
	akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
	linus.walleij@...aro.org, nicolas.iooss_linux@....org,
	pmladek@...e.com, tj@...nel.org
Subject: Re: [PATCH v4 4/4] pr_emerg add WARN_XX() debugger options

On Mon,  1 Feb 2016 16:35:52 -0700
Jeffrey Merkey <jeffmerkey@...il.com> wrote:
> ---
>  include/linux/printk.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/include/linux/printk.h b/include/linux/printk.h
> index 51dd6b8..dcfb270 100644
> --- a/include/linux/printk.h
> +++ b/include/linux/printk.h
> @@ -252,8 +252,16 @@ extern asmlinkage void dump_stack(void) __cold;
>   * and other debug macros are compiled out unless either DEBUG is defined
>   * or CONFIG_DYNAMIC_DEBUG is set.
>   */
> +#ifdef CONFIG_DEBUG_WARN
> +#define pr_emerg(fmt, ...) \
> +({								\
> +	printk(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__);		\
> +	BUG();							\

This look rather heavy handed for a debug feature. This will crash any
kernel on a pr-emerg(), similar to a panic on warning. Not only that,
for cases that cal pr_emerg() more than once, it crashes on the first
instance.

What about adding a condition that can be set set in /proc/sys/kernel/
A file called something like crash_on_print_emerg ?

	BUG_ON(crash_on_pr_emerg);

-- Steve

> +})
> +#else
>  #define pr_emerg(fmt, ...) \
>  	printk(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__)
> +#endif
>  #define pr_alert(fmt, ...) \
>  	printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
>  #define pr_crit(fmt, ...) \