From: Dave Hansen <dave.hansen@intel.com>
To: Sean Christopherson <seanjc@google.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org, keescook@chromium.org
Subject: Re: [PATCH] x86/mm: Refuse W^X violations
Date: Thu, 25 Aug 2022 10:38:23 -0700 [thread overview]
Message-ID: <2f862d0f-e851-0de3-a789-991448ed8b68@intel.com> (raw)
In-Reply-To: <Yweu1dvkJ8aV+C+T@google.com>
On 8/25/22 10:18, Sean Christopherson wrote:
>> +/*
>> + * Validate and enforce strict W^X semantics.
>> + */
>> +static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long start,
>> + unsigned long pfn, unsigned long npg)
>> +{
>> + unsigned long end;
>> +
> I think this needs
>
> if (!(__supported_pte_mask & _PAGE_NX))
> return new;
>
> to play nice with non-PAE 32-bit kernels.
Good catch. Nit: I'd probably write this up as:
if (!cpu_feature_enabled(X86_FEATURE_NX))
return new;
That gets us our fancy static branches and is a bit easier on the eyes.
I checked and don't see a way for __supported_pte_mask to have _PAGE_NX
clear when X86_FEATURE_NX==1.
next prev parent reply other threads:[~2022-08-25 17:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-25 12:23 [PATCH] x86/mm: Refuse W^X violations Peter Zijlstra
2022-08-25 17:18 ` Sean Christopherson
2022-08-25 17:38 ` Dave Hansen [this message]
2022-08-25 18:16 ` Kees Cook
2022-08-25 19:42 ` Peter Zijlstra
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