linux-kernel - Re: [PATCH v3 2/2] locking/percpu-rwsem: Annotate rwsem ownership transfer by setting RWSEM_OWNER

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: <e011289a-e13a-8839-7a48-eb6e58f5eaa7@redhat.com>
Date:   Tue, 15 May 2018 14:45:57 -0400
From:   Waiman Long <longman@...hat.com>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Theodore Y. Ts'o" <tytso@....edu>,
        Oleg Nesterov <oleg@...hat.com>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v3 2/2] locking/percpu-rwsem: Annotate rwsem ownership
 transfer by setting RWSEM_OWNER_UNKNOWN

On 05/15/2018 02:05 PM, Amir Goldstein wrote:
> On Tue, May 15, 2018 at 9:02 PM, Waiman Long <longman@...hat.com> wrote:
>> On 05/15/2018 01:58 PM, Peter Zijlstra wrote:
>>> On Tue, May 15, 2018 at 01:38:04PM -0400, Waiman Long wrote:
>>>> +/*
>>>> + * Owner value to indicate the rwsem's owner is not currently known.
>>>> + */
>>>> +#define RWSEM_OWNER_UNKNOWN ((struct task_struct *)-1)
>>> It might be nice to comment that this works and relies on having that
>>> ANON_OWNER bit set.
>> I am just trying not to expose internal working of rwsem, but I can
>> document that one of the bits is the real deal without specifying which one.
>>
> BUILD_BUG_ON(!rwsem_has_anonymous_owner(RWSEM_OWNER_UNKNOWN))
> inside rwsem.c and comment above to explain it.

Yes, it is a good idea. I will do that.

-Longman