linux-kernel - Re: [PATCH] riscv: read-only pages should not be writable

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Message-ID: <CAMj1kXGmwwD==yOnzfYgPg8Bpz1POK7aPBULcuMdgS-E1G2EAw@mail.gmail.com>
Date:   Sat, 28 May 2022 11:13:07 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atishp@...shpatra.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] riscv: read-only pages should not be writable

On Sat, 28 May 2022 at 03:41, Heinrich Schuchardt
<heinrich.schuchardt@...onical.com> wrote:
>
> If EFI pages are marked as read-only,
> we should remove the _PAGE_WRITE flag.
>
> The current code overwrites an unused value.
>
> Fixes: b91540d52a08b ("RISC-V: Add EFI runtime services")
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
> ---
>  arch/riscv/kernel/efi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/efi.c b/arch/riscv/kernel/efi.c
> index 024159298231..1aa540350abd 100644
> --- a/arch/riscv/kernel/efi.c
> +++ b/arch/riscv/kernel/efi.c
> @@ -65,7 +65,7 @@ static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
>
>         if (md->attribute & EFI_MEMORY_RO) {
>                 val = pte_val(pte) & ~_PAGE_WRITE;
> -               val = pte_val(pte) | _PAGE_READ;
> +               val |= _PAGE_READ;
>                 pte = __pte(val);
>         }
>         if (md->attribute & EFI_MEMORY_XP) {
> --
> 2.36.1
>

Thanks Heinrich

Queued in efi/urgent.