linux-kernel - Re: [PATCH v4 2/2] sched: Skip priority checks with SCHED_FLAG_KEEP

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: <787ac8b6-3df6-0225-e835-c17a56a8d642@arm.com>
Date:   Thu, 29 Jul 2021 19:31:12 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Quentin Perret <qperret@...gle.com>
Cc:     mingo@...hat.com, peterz@...radead.org, vincent.guittot@...aro.org,
        qais.yousef@....com, rickyiu@...gle.com, wvw@...gle.com,
        patrick.bellasi@...bug.net, xuewen.yan94@...il.com,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH v4 2/2] sched: Skip priority checks with
 SCHED_FLAG_KEEP_PARAMS

On 26/07/2021 15:56, Quentin Perret wrote:
> On Thursday 22 Jul 2021 at 10:47:33 (+0200), Dietmar Eggemann wrote:

[...]

>>> @@ -7393,6 +7403,8 @@ SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
>>>  	rcu_read_unlock();
>>>  
>>>  	if (likely(p)) {
>>> +		if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS)
>>> +			get_params(p, &attr);
>>
>> SCHED_FLAG_KEEP_PARAMS is handled here but SCHED_FLAG_KEEP_POLICY
>> outside (before) the `if (likely(p))`?
> 
> Because I need to dereference p while SCHED_FLAG_KEEP_POLICY doesn't :)

Ah, true. Looked weird though.
But then the SCHED_FLAG_KEEP_POLICY condition can be placed closer to
the SCHED_FLAG_KEEP_PARAMS condition. We don't have to set
SETPARAM_POLICY if p == NULL.

>>>  		retval = sched_setattr(p, &attr);
>>>  		put_task_struct(p);
>>>  	}

[...]