linux-kernel - Re: [PATCH v2] powerpc/32s: Fix random crashes by adding isync() after locking/unlocking KUEP

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Date:   Fri, 27 Aug 2021 23:25:00 +1000
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        fthain@...ux-m68k.org, userm57@...oo.com,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] powerpc/32s: Fix random crashes by adding isync() after locking/unlocking KUEP

On Wed, 18 Aug 2021 06:49:29 +0000 (UTC), Christophe Leroy wrote:
> Commit b5efec00b671 ("powerpc/32s: Move KUEP locking/unlocking in C")
> removed the 'isync' instruction after adding/removing NX bit in user
> segments. The reasoning behind this change was that when setting the
> NX bit we don't mind it taking effect with delay as the kernel never
> executes text from userspace, and when clearing the NX bit this is
> to return to userspace and then the 'rfi' should synchronise the
> context.
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/32s: Fix random crashes by adding isync() after locking/unlocking KUEP
      https://git.kernel.org/powerpc/c/ef486bf448a057a6e2d50e40ae879f7add6585da

cheers