linux-kernel - Re: [PATCH] powerpc/32s: Fix kuap_kernel

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Message-Id: <163369938390.3568929.9026666512859787724.b4-ty@ellerman.id.au>
Date:   Sat, 09 Oct 2021 00:23:03 +1100
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     Finn Thain <fthain@...ux-m68k.org>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, Stan Johnson <userm57@...oo.com>
Subject: Re: [PATCH] powerpc/32s: Fix kuap_kernel_restore()

On Wed, 15 Sep 2021 16:12:24 +0200, Christophe Leroy wrote:
> At interrupt exit, kuap_kernel_restore() calls kuap_unclok() with the
> value contained in regs->kuap. However, when regs->kuap contains
> 0xffffffff it means that KUAP was not unlocked so calling
> kuap_unlock() is unrelevant and results in jeopardising the contents
> of kernel space segment registers.
> 
> So check that regs->kuap doesn't contain KUAP_NONE before calling
> kuap_unlock(). In the meantime it also means that if KUAP has not
> been correcly locked back at interrupt exit, it must be locked
> before continuing. This is done by checking the content of
> current->thread.kuap which was returned by kuap_get_and_assert_locked()
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/32s: Fix kuap_kernel_restore()
      https://git.kernel.org/powerpc/c/d93f9e23744b7bf11a98b2ddb091d129482ae179

cheers