From: Andy Lutomirski <luto@kernel.org>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>,
X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Juergen Gross <jgross@suse.com>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>, Jiri Kosina <jkosina@suse.cz>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Brian Gerst <brgerst@gmail.com>,
David Laight <David.Laight@aculab.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
Eduardo Valentin <eduval@amazon.com>,
Greg KH <gregkh@linuxfoundation.org>,
Will Deacon <will.deacon@arm.com>,
"Liguori, Anthony" <aliguori@amazon.com>,
Daniel Gruss <daniel.gruss@iaik.tugraz.at>,
Hugh Dickins <hughd@google.com>, Kees Cook <keescook@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Waiman Long <llong@redhat.com>, Pavel Machek <pavel@ucw.cz>,
"David H . Gutteridge" <dhgutteridge@sympatico.ca>,
Joerg Roedel <jroedel@suse.de>
Subject: Re: [PATCH 2/3] x86/mm/pti: Don't clear permissions in pti_clone_pmd()
Date: Tue, 7 Aug 2018 12:38:24 -0700 [thread overview]
Message-ID: <CALCETrXj1-CC-rcnM5s2SvbSFKjZPMYj0O-9d1PY0MRdGEKs-g@mail.gmail.com> (raw)
In-Reply-To: <feea2aff-91ff-89a6-9d7c-5402a1d6a27f@intel.com>
On Tue, Aug 7, 2018 at 11:34 AM, Dave Hansen <dave.hansen@intel.com> wrote:
> On 08/07/2018 03:24 AM, Joerg Roedel wrote:
>> The function sets the global-bit on cloned PMD entries,
>> which only makes sense when the permissions are identical
>> between the user and the kernel page-table.
>>
>> Further, only write-permissions are cleared for entry-text
>> and kernel-text sections, which are not writeable anyway.
>
> I think this patch is correct, but I'd be curious if Andy remembers why
> we chose to clear _PAGE_RW on these things. It might have been that we
> were trying to say that the *entry* code shouldn't write to this stuff,
> regardless of whether the normal kernel can.
>
> But, either way, I agree with the logic here that Global pages must
> share permissions between both mappings, so feel free to add my Ack. I
> just want to make sure Andy doesn't remember some detail I'm forgetting.
I suspect it's because we used to (and maybe still do) initialize the
user tables before mark_read_only().
next prev parent reply other threads:[~2018-08-07 19:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-07 10:24 [PATCH 0/3] PTI for x86-32 Fixes Joerg Roedel
2018-08-07 10:24 ` [PATCH 1/3] x86/mm/pti: Fix 32 bit PCID check Joerg Roedel
2018-08-07 10:24 ` [PATCH 2/3] x86/mm/pti: Don't clear permissions in pti_clone_pmd() Joerg Roedel
2018-08-07 18:34 ` Dave Hansen
2018-08-07 19:38 ` Andy Lutomirski [this message]
2018-08-07 20:21 ` Thomas Gleixner
2018-08-07 20:28 ` Andy Lutomirski
2018-08-07 10:24 ` [PATCH 3/3] x86/mm/pti: Clone kernel-image on PTE level for 32 bit Joerg Roedel
2018-08-17 2:44 ` [PATCH 0/3] PTI for x86-32 Fixes David H. Gutteridge
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