linux-kernel - Re: [PATCH 2/4] livepatch: Handle failing allocation of shadow variables in the selftest

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]

Message-ID: <20190130085622.y4de47nekrhy4pmq@pathway.suse.cz>
Date:   Wed, 30 Jan 2019 09:56:22 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Joe Lawrence <joe.lawrence@...hat.com>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Jason Baron <jbaron@...mai.com>,
        Evgenii Shatokhin <eshatokhin@...tuozzo.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] livepatch: Handle failing allocation of shadow
 variables in the selftest

On Mon 2019-01-21 17:40:12, Joe Lawrence wrote:
> On Wed, Jan 16, 2019 at 05:17:18PM +0100, Petr Mladek wrote:
> > Do not dereference pointers to the shadow variables when either
> > klp_shadow_alloc() or klp_shadow_get() fail.
> > 
> > There is no need to check the other locations explicitly. The test
> > would fail if any allocation fails. And the existing messages, printed
> > during the test, provide enough information to debug eventual problems.
> > 
> 
> I didn't run the test under those failing conditions, but at looking at
> the code, I think it would simply skip the "expected <conditions> found"
> and the test script would complain about not seeing that msg.

Accessing an invalid pointer would crash the kernel.


> Would it be easier to just bite the bullet and verify sv[0-4] at their
> allocation sites?  Then later uses (ie, the sv3 dereference that
> Miroslav spotted at the bottom) or new code wouldn't fall through the
> cracks.

As I wrote in the replay to Miroslav. The best practice is to
handle errors everywhere. I am going to do so in v2. People
might use it as a sample...

Best Regards,
Petr