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

[Palmer Dabbelt]

On Tue, 31 May 2022 00:56:52 PDT (-0700), coelacanthus at 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 at outlook.com>
> Co-developed-by: dram <dramforever at live.com>
> Signed-off-by: dram <dramforever at live.com>
> Co-developed-by: Ruizhe Pan <c141028 at gmail.com>
> Signed-off-by: Ruizhe Pan <c141028 at gmail.com>
> Signed-off-by: Celeste Liu <coelacanthus at outlook.com>
> Cc: linux-riscv at lists.infradead.org
> Cc: Palmer Dabbelt <palmer at 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.