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From: Petr Mladek <pmladek@suse.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	"Tobin C . Harding" <me@tobin.cc>, Joe Perches <joe@perches.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.cz>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 10/11] vsprintf: WARN() on invalid pointer access
Date: Fri, 27 Apr 2018 14:37:53 +0200	[thread overview]
Message-ID: <20180427123753.22mctekbwocbpfwj@pathway.suse.cz> (raw)
In-Reply-To: <20180426012805.GA3282@jagdpanzerIV>

On Thu 2018-04-26 10:28:05, Sergey Senozhatsky wrote:
> On (04/25/18 13:12), Petr Mladek wrote:
> [..]
> >   /*
> >    * This is not a fool-proof test. 99% of the time that this will fault is
> >    * due to a bad pointer, not one that crosses into bad memory. Just test
> > @@ -623,8 +626,12 @@ static const char *check_pointer_access(const void *ptr)
> >  	if (!ptr)
> >  		return "(null)";
> >  
> > -	if (probe_kernel_address(ptr, byte))
> > +	/* Prevent silent crashes when called in printk_safe context. */
> > +	if (probe_kernel_address(ptr, byte)) {
> > +		WARN(!panic_on_warn && !test_printf_pointer_access,
> > +		     "vsprintf: invalid pointer address\n");
> >  		return "(efault)";
> > +	}
> 
> Can we have a rate-limited print out here? Or may be even a WARN_ONCE()?
> Yes, printk()-s from check_pointer_access() are OK, printk_safe() helps us,
> but at the same time every single invalid pointer access printk()-message
> will log_store() WARN() extra entries. Theoretically, this can harm. What
> do you think?

I believe that these WARNs will be rare. After all they happen in situations
where the kernel crashed so far.

I suggest to keep it as is for now. We could always ratelimit it later if
needed.

Best Regards,
Petr

  reply	other threads:[~2018-04-27 12:37 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-25 11:12 [PATCH v5 00/11] vsprintf: Prevent silent crashes and consolidate error handling Petr Mladek
2018-04-25 11:12 ` [PATCH v5 01/11] vsprintf: Shuffle misc pointer to string functions Petr Mladek
2018-04-25 14:57   ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 02/11] vsprintf: Add missing const ptr qualifier to prt_to_id() Petr Mladek
2018-04-25 14:57   ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 03/11] vsprintf: Consistent %pK handling for kptr_restrict == 0 Petr Mladek
2018-04-25 14:58   ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 04/11] vsprintf: Do not check address of well-known strings Petr Mladek
2018-04-25 11:44   ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 05/11] vsprintf: Consolidate handling of unknown pointer specifiers Petr Mladek
2018-04-25 13:08   ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 06/11] vsprintf: Factor out %p[iI] handler as ip_addr_string() Petr Mladek
2018-04-25 13:11   ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 07/11] vsprintf: Factor out %pV handler as va_format() Petr Mladek
2018-04-25 14:56   ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 08/11] vsprintf: Factor out %pO handler as kobject_string() Petr Mladek
2018-04-25 15:01   ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 09/11] vsprintf: Prevent crash when dereferencing invalid pointers Petr Mladek
2018-04-25 15:10   ` Andy Shevchenko
2018-04-25 15:32     ` Andy Shevchenko
2018-04-27 12:47     ` Petr Mladek
2018-05-03 11:55       ` Andy Shevchenko
2018-04-26 21:46   ` kbuild test robot
2018-04-25 11:12 ` [PATCH v5 10/11] vsprintf: WARN() on invalid pointer access Petr Mladek
2018-04-25 12:43   ` Rasmus Villemoes
2018-04-26  1:28   ` Sergey Senozhatsky
2018-04-27 12:37     ` Petr Mladek [this message]
2018-04-25 11:12 ` [PATCH v5 11/11] vsprintf: Avoid confusion between invalid address and value Petr Mladek
2018-04-27 14:10 ` [PATCH v5 00/11] vsprintf: Prevent silent crashes and consolidate error handling Petr Mladek

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