From: Peter Zijlstra <peterz@infradead.org>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Nadav Amit <namit@vmware.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Xu <peterx@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>, Yu Zhao <yuzhao@google.com>,
Nick Piggin <npiggin@gmail.com>,
x86@kernel.org
Subject: Re: [PATCH v2 3/5] x86/mm: check exec permissions on fault
Date: Mon, 25 Oct 2021 12:59:56 +0200 [thread overview]
Message-ID: <YXaOLAIo7B0+1NUc@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20211021122112.592634-4-namit@vmware.com>
On Thu, Oct 21, 2021 at 05:21:10AM -0700, Nadav Amit wrote:
> From: Nadav Amit <namit@vmware.com>
> Add a check to prevent access_error() from returning mistakenly that
> page-faults due to instruction fetch are not allowed. Intel SDM does not
> indicate whether "instruction fetch" and "write" in the hardware error
> code are mutual exclusive, so check both before returning whether the
> access is allowed.
Dave, can we get that clarified? It seems a bit naf and leads to
confusing code IMO.
Other than that, the change looks ok to me.
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index b2eefdefc108..e776130473ce 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1100,10 +1100,17 @@ access_error(unsigned long error_code, struct vm_area_struct *vma)
> (error_code & X86_PF_INSTR), foreign))
> return 1;
>
> - if (error_code & X86_PF_WRITE) {
> + if (error_code & (X86_PF_WRITE | X86_PF_INSTR)) {
> /* write, present and write, not present: */
> - if (unlikely(!(vma->vm_flags & VM_WRITE)))
> + if ((error_code & X86_PF_WRITE) &&
> + unlikely(!(vma->vm_flags & VM_WRITE)))
> return 1;
> +
> + /* exec, present and exec, not present: */
> + if ((error_code & X86_PF_INSTR) &&
> + unlikely(!(vma->vm_flags & VM_EXEC)))
> + return 1;
> +
> return 0;
> }
next prev parent reply other threads:[~2021-10-25 11:00 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-21 12:21 [PATCH v2 0/5] mm/mprotect: avoid unnecessary TLB flushes Nadav Amit
2021-10-21 12:21 ` [PATCH v2 1/5] x86: Detection of Knights Landing A/D leak Nadav Amit
2021-10-26 15:54 ` Dave Hansen
2021-10-26 15:57 ` Nadav Amit
2021-10-21 12:21 ` [PATCH v2 2/5] mm: avoid unnecessary flush on change_huge_pmd() Nadav Amit
2021-10-25 10:52 ` Peter Zijlstra
2021-10-25 16:29 ` Nadav Amit
2021-10-26 16:06 ` Dave Hansen
2021-10-26 16:47 ` Nadav Amit
2021-10-26 16:53 ` Nadav Amit
2021-10-26 17:44 ` Nadav Amit
2021-10-26 18:44 ` Dave Hansen
2021-10-26 19:06 ` Nadav Amit
2021-10-26 19:40 ` Dave Hansen
2021-10-26 20:07 ` Nadav Amit
2021-10-26 20:47 ` Dave Hansen
2021-10-21 12:21 ` [PATCH v2 3/5] x86/mm: check exec permissions on fault Nadav Amit
2021-10-25 10:59 ` Peter Zijlstra [this message]
2021-10-25 11:13 ` Andrew Cooper
2021-10-25 14:23 ` Dave Hansen
2021-10-25 14:20 ` Dave Hansen
2021-10-25 16:19 ` Nadav Amit
2021-10-25 17:45 ` Dave Hansen
2021-10-25 17:51 ` Nadav Amit
2021-10-25 18:00 ` Dave Hansen
2021-10-21 12:21 ` [PATCH v2 4/5] mm/mprotect: use mmu_gather Nadav Amit
2021-10-21 12:21 ` [PATCH v2 5/5] mm/mprotect: do not flush on permission promotion Nadav Amit
2021-10-25 11:12 ` Peter Zijlstra
2021-10-25 16:27 ` Nadav Amit
2021-10-22 3:04 ` [PATCH v2 0/5] mm/mprotect: avoid unnecessary TLB flushes Andrew Morton
2021-10-22 21:58 ` Nadav Amit
2021-10-26 16:09 ` Dave Hansen
2021-10-25 10:50 ` Peter Zijlstra
2021-10-25 16:42 ` Nadav Amit
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