linux-kernel - Re: Kernel crash due to memory corruption with v5.4.26-rt17 and PowerPC e500

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Message-ID: <20200901074107.ozrthr5piqu723pa@linutronix.de>
Date:   Tue, 1 Sep 2020 09:41:07 +0200
From:   'Sebastian Andrzej Siewior' <bigeasy@...utronix.de>
To:     Thomas Graziadei <thomas.graziadei@...cronenergy.com>
Cc:     Mark Marshall <markmarshall14@...il.com>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Mark Marshall <mark.marshall@...cronenergy.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>
Subject: Re: Kernel crash due to memory corruption with v5.4.26-rt17 and
 PowerPC e500

On 2020-08-12 14:45:22 [+0200], Thomas Graziadei wrote:
> Hi Sebastian,
Hi Thomas,

> any progress on your side?
> 
> Do you think the patch could be applied for the next versions?

Yes.  The ->active_mm change needs to be protected against scheduling
regardless of the arch/mmu. Otherwise the mm will be put twice. For this
to trigger you need to exec from a kernel thread and get preempted.
This will be addressed in use_mm() by commit
    38cf307c1f201 ("mm: fix kthread_use_mm() vs TLB invalidate")

which is in v5.9-rc1 and exec_mmap() is under discussion at
    https://lore.kernel.org/linux-arch/20200828100022.1099682-2-npiggin@gmail.com/

> Regards,
> Thomas

Sebastian