Re: [PATCH] arm64: mte: fix prctl(PR_GET_TAGGED_ADDR_CTRL) if TCF0=NONE

From: Catalin Marinas <catalin.marinas@arm.com>
To: Peter Collingbourne <pcc@google.com>
Cc: Will Deacon <will@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64: mte: fix prctl(PR_GET_TAGGED_ADDR_CTRL) if TCF0=NONE
Date: Thu, 3 Dec 2020 14:51:31 +0000	[thread overview]
Message-ID: <20201203145131.GB2830@gaia> (raw)
In-Reply-To: <20201203075110.2781021-1-pcc@google.com>

On Wed, Dec 02, 2020 at 11:51:10PM -0800, Peter Collingbourne wrote:
> Previously we were always returning a tag inclusion mask of zero via
> PR_GET_TAGGED_ADDR_CTRL if TCF0 was set to NONE. Fix it by making
> the code for the NONE case match the others.
> 
> Signed-off-by: Peter Collingbourne <pcc@google.com>
> Link: https://linux-review.googlesource.com/id/Iefbea66cf7d2b4c80b82f9639b9ea7f33f7fac53
> ---
>  arch/arm64/kernel/mte.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> index 52a0638ed967..ef15c8a2a49d 100644
> --- a/arch/arm64/kernel/mte.c
> +++ b/arch/arm64/kernel/mte.c
> @@ -189,7 +189,8 @@ long get_mte_ctrl(struct task_struct *task)
>  
>  	switch (task->thread.sctlr_tcf0) {
>  	case SCTLR_EL1_TCF0_NONE:
> -		return PR_MTE_TCF_NONE;
> +		ret |= PR_MTE_TCF_NONE;
> +		break;
>  	case SCTLR_EL1_TCF0_SYNC:
>  		ret |= PR_MTE_TCF_SYNC;
>  		break;

With a fixes tag:

Fixes: af5ce95282dc ("arm64: mte: Allow user control of the generated random tags via prctl()")
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

Will, if you have another pull request for 5.10, please pick this up as
well (it's an ABI fix so it would be nice to get it in the first release
with MTE support). Otherwise I'll queue it at -rc1 and cc stable.

Thanks.

-- 
Catalin

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