From: Linus Torvalds <torvalds@linux-foundation.org>
To: David Laight <David.Laight@aculab.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Will Deacon <will@kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Waiman Long <longman@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Andy Lutomirski <luto@kernel.org>, Christoph Hellwig <hch@lst.de>,
Mark Rutland <mark.rutland@arm.com>,
Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH v4 3/4] x86/uaccess: Use pointer masking to limit uaccess speculation
Date: Wed, 5 May 2021 11:32:17 -0700 [thread overview]
Message-ID: <CAHk-=wh-a6B11tH3upLG+-P5_yFPs3PB8tiXO5JKaQjUvhOMYg@mail.gmail.com> (raw)
In-Reply-To: <2f75c496ac774444b75ff808854b8e5f@AcuMS.aculab.com>
On Wed, May 5, 2021 at 1:48 AM David Laight <David.Laight@aculab.com> wrote:
>
> This would error requests for address 0 earlier - but I don't
> believe they are ever valid in Linux.
> (Some historic x86 a.out formats did load to address 0.)
Not only loading at address 0 - there are various real reason s why
address 0 might actually be needed.
Anybody who still runs a 32-bit kernel and wants to use vm86 mode, for
example, requires address 0 because that's simply how the hardware
works.
So no. "mask to zero and make zero invalid" is not a proper model.
Linus
next prev parent reply other threads:[~2021-05-05 18:32 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-05 3:54 [PATCH v4 0/4] x86/uaccess: Use pointer masking to limit uaccess speculation Josh Poimboeuf
2021-05-05 3:54 ` [PATCH v4 1/4] uaccess: Always inline strn*_user() helper functions Josh Poimboeuf
2021-05-05 3:54 ` [PATCH v4 2/4] uaccess: Fix __user annotations for copy_mc_to_user() Josh Poimboeuf
2021-05-05 3:54 ` [PATCH v4 3/4] x86/uaccess: Use pointer masking to limit uaccess speculation Josh Poimboeuf
2021-05-05 8:48 ` David Laight
2021-05-05 13:19 ` Josh Poimboeuf
2021-05-05 13:51 ` David Laight
2021-05-05 18:32 ` Linus Torvalds [this message]
2021-05-06 7:57 ` David Laight
2021-05-05 14:25 ` Mark Rutland
2021-05-05 14:48 ` Josh Poimboeuf
2021-05-05 14:49 ` David Laight
2021-05-05 15:45 ` Mark Rutland
2021-05-05 16:55 ` Andy Lutomirski
2021-05-06 8:36 ` David Laight
2021-05-06 12:05 ` Christoph Hellwig
2021-06-02 17:11 ` Sean Christopherson
2021-06-02 20:11 ` Josh Poimboeuf
2021-05-05 3:54 ` [PATCH v4 4/4] x86/nospec: Remove barrier_nospec() Josh Poimboeuf
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