Re: [PATCH] riscv: mmap with PROT_WRITE but no PROT_READ is invalid

From: Palmer Dabbelt <palmer@dabbelt.com>
To: coelacanthus@outlook.com
Cc: linux-riscv@lists.infradead.org, coelacanthus@outlook.com,
	xc-tan@outlook.com, dramforever@live.com, c141028@gmail.com
Subject: Re: [PATCH] riscv: mmap with PROT_WRITE but no PROT_READ is invalid
Date: Thu, 21 Jul 2022 16:19:57 -0700 (PDT)	[thread overview]
Message-ID: <mhng-4904215b-4d85-4886-8eb3-bdd363447cf0@palmer-mbp2014> (raw)
In-Reply-To: <PH7PR14MB559464DBDD310E755F5B21E8CEDC9@PH7PR14MB5594.namprd14.prod.outlook.com>

On Tue, 31 May 2022 00:56:52 PDT (-0700), coelacanthus@outlook.com wrote:
> As mentioned in Table 4.5 in RISC-V spec Volume 2 Section 4.3, write
> but not read is "Reserved for future use.". For now, they are not valid.
> In the current code, -wx is marked as invalid, but -w- is not marked
> as invalid.
> This patch refines that judgment.
>
> Reported-by: xctan <xc-tan@outlook.com>
> Co-developed-by: dram <dramforever@live.com>
> Signed-off-by: dram <dramforever@live.com>
> Co-developed-by: Ruizhe Pan <c141028@gmail.com>
> Signed-off-by: Ruizhe Pan <c141028@gmail.com>
> Signed-off-by: Celeste Liu <coelacanthus@outlook.com>
> Cc: linux-riscv@lists.infradead.org
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> ---
>  arch/riscv/kernel/sys_riscv.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
> index 12f8a7fce78b..8a7880b9c433 100644
> --- a/arch/riscv/kernel/sys_riscv.c
> +++ b/arch/riscv/kernel/sys_riscv.c
> @@ -18,9 +18,8 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len,
>  	if (unlikely(offset & (~PAGE_MASK >> page_shift_offset)))
>  		return -EINVAL;
>
> -	if ((prot & PROT_WRITE) && (prot & PROT_EXEC))
> -		if (unlikely(!(prot & PROT_READ)))
> -			return -EINVAL;
> +	if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ)))
> +		return -EINVAL;
>
>  	return ksys_mmap_pgoff(addr, len, prot, flags, fd,
>  			       offset >> (PAGE_SHIFT - page_shift_offset));

Thanks, this is on for-next.

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