linux-kernel - Re: [PATCH] powerpc/vdso: Fix VDSO unmap check

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Date:   Thu, 10 Mar 2022 17:18:29 +0100
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH] powerpc/vdso: Fix VDSO unmap check

On 09/03/2022, 16:51:04, Christophe Leroy wrote:
> 
> 
> Le 03/11/2020 à 18:13, Laurent Dufour a écrit :
>> The check introduced by the commit 83d3f0e90c6c ("powerpc/mm: tracking vDSO
>> remap") is wrong and is missing some partial unmaps of the VDSO.
>>
>> To be complete the check needs the base and end address of the
>> VDSO. Currently only the base is available in the mm_context of a task, but
>> the end address can easily be computed because the size of VDSO is
>> constant. However, there are 2 sizes for 32 or 64 bits task and they are
>> stored in static variables in arch/powerpc/kernel/vdso.c.
>>
>> Exporting a new function called vdso_pages() to get the number of pages of
>> the VDSO based on the static variables from arch/powerpc/kernel/vdso.c.
>>
>> Fixes: 83d3f0e90c6c ("powerpc/mm: tracking vDSO remap")
>>
>> Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
>> Reported-by: Thomas Gleixner <tglx@...utronix.de>
>> Suggested-by: Christophe Leroy <christophe.leroy@...roup.eu>
>> Cc: Michael Ellerman <mpe@...erman.id.au>
>> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> Cc: Paul Mackerras <paulus@...ba.org>
>> ---
>>   arch/powerpc/include/asm/mmu_context.h | 18 ++++++++++++++++--
>>   arch/powerpc/kernel/vdso.c             | 14 ++++++++++++++
>>   2 files changed, 30 insertions(+), 2 deletions(-)
> 
> This patch doesn't apply anymore.
> 
> In the meantime there's a pending series from Dmitry, so I'm wondering if
> it is worth rebasing this series or not.

I agee, the Dimitry's series looks better, addressing the issue in the
common code for all the architectures.

Laurent.