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Date:   Sun, 16 May 2021 14:01:29 +0100
From:   Khaled Romdhani <khaledromdhani216@gmail.com>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     mingo@redhat.com, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com, linux-kernel@vger.kernel.org,
        kernel-janitors@vger.kernel.org
Subject: Re: [PATCH-next] sched: Fix Null pointer derefrence
Message-ID: <20210516130129.GA32445@ard0534>
References: <20210515164645.22849-1-khaledromdhani216@gmail.com>
 <20210515210238.GG5618@worktop.programming.kicks-ass.net>
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On Sat, May 15, 2021 at 11:02:38PM +0200, Peter Zijlstra wrote:
> On Sat, May 15, 2021 at 05:46:45PM +0100, Khaled ROMDHANI wrote:
> > The 'curr' variable could be NULL and derefrenced by
> > pick_next_entity. Fix this by adding a check that prevent
> > the invocation of pick_next_entity with a NULL passed argument.
> 
> And why exactly is that a problem?
>
Within pick_next_entity, we could have 'left = curr'. 
Thus the function wakeup_preempt_entity which is invoked 
from pick_next_entity, derefrence the the sched entity 'left' 
that may be a NULL passed argument.