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

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Message-ID: <7b93efe6-fb54-d6f8-dd3b-3fb260652f15@canonical.com>
Date:   Sat, 28 May 2022 11:26:28 +0200
From:   Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
To:     Ard Biesheuvel <ardb@...nel.org>
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>,
        stable@...r.kernel.org
Subject: Re: [PATCH] riscv: read-only pages should not be writable



On 5/28/22 11:13, Ard Biesheuvel wrote:
> 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.

I guess this should also be down-ported to 5.15 and 5.10.

Best regards

Heinrich