From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Peter Zijlstra <peterz@infradead.org>, 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 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 12:13:54 +0100 [thread overview]
Message-ID: <73f3ff27-861f-ebd9-ae89-8fa4e206bc2d@citrix.com> (raw)
In-Reply-To: <YXaOLAIo7B0+1NUc@hirez.programming.kicks-ass.net>
On 25/10/2021 11:59, Peter Zijlstra wrote:
> 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.
There is no such thing as an instruction fetch (a read) causing a
modification to the mapping. From this point of view, you'd never
expect to see them both set.
However, be aware that INSTR is only reported for NX || SMEP. Without
either, instruction vs data accesses are distinguished internally (can
be demonstrated with SMAP) but not visible in the pagefault error code.
~Andrew
next prev parent reply other threads:[~2021-10-25 11:14 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
2021-10-25 11:13 ` Andrew Cooper [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=73f3ff27-861f-ebd9-ae89-8fa4e206bc2d@citrix.com \
--to=andrew.cooper3@citrix.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=dave.hansen@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=nadav.amit@gmail.com \
--cc=namit@vmware.com \
--cc=npiggin@gmail.com \
--cc=peterx@redhat.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=will@kernel.org \
--cc=x86@kernel.org \
--cc=yuzhao@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.