linux-kernel - Re: [PATCH] lib: Add test module for CONFIG_DEBUG

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:   Tue, 8 Aug 2017 20:35:05 +0200
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        ard.biesheuvel@...aro.org, labbott@...hat.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Kees Cook <keescook@...omium.org>,
        Ingo Molnar <mingo@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Olof Johansson <olof@...om.net>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Ts'o <tytso@....edu>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jiri Pirko <jiri@...lanox.com>,
        Jeff Layton <jlayton@...hat.com>
Subject: Re: [PATCH] lib: Add test module for CONFIG_DEBUG_VIRTUAL

On Tue, Aug 08, 2017 at 11:04:11AM -0700, Florian Fainelli wrote:
> On 08/08/2017 10:57 AM, Luis R. Rodriguez wrote:
> > On Tue, Aug 08, 2017 at 09:40:26AM -0700, Florian Fainelli wrote:
> >> Add a test module that allows testing that CONFIG_DEBUG_VIRTUAL works
> >> correctly, at least that it can catch invalid calls to virt_to_phys()
> >> against the non-linear kernel virtual address map.
> >>
> >> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> >> ---
> 
> >> +static int __init test_debug_virtual_init(void)
> >> +{
> >> +	phys_addr_t pa;
> >> +	void *va;
> >> +
> >> +	va = (void *)VMALLOC_START;
> >> +	pa = virt_to_phys(va);
> >> +
> >> +	pr_info("PA: %pa for VA: 0x%lx\n", &pa, (unsigned long)va);
> >> +
> >> +	foo = kzalloc(sizeof(*foo), GFP_KERNEL);
> >> +	if (!foo)
> >> +		return -ENOMEM;
> >> +
> >> +	pa = virt_to_phys(foo);
> >> +	va = foo;
> >> +	pr_info("PA: %pa for VA: 0x%lx\n", &pa, (unsigned long)va);
> > 
> > Should there be a tests here of some sort? When should this fail, why?
> 
> There is no test per-se, the kernel will produce warning with
> CONFIG_DEBUG_VIRTUAL telling you that what you are doing is wrong.
> 
> > There is no docs on this self test, could one be added?
> 
> I suppose I could add one even though that just means pointing out the
> code that produces the warning?

A /* note */ indicating what you just said above would suffice then but
typically tests return back to userspace an error, so another option
would be to see if one could get a return value that an error happened
and return that back to the module init. Grepping just for warning for
an error seems error prone.

  Luis