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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: David Laight <David.Laight@aculab.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.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>,
	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 09:48:22 -0500	[thread overview]
Message-ID: <20210505144822.muxfkxo5vajzgycu@treble> (raw)
In-Reply-To: <20210505142542.GC5605@C02TD0UTHF1T.local>

On Wed, May 05, 2021 at 03:25:42PM +0100, Mark Rutland wrote:
> On arm64 we needed to have a sequence here because the addr_limit used
> to be variable, but now that we've removed set_fs() and split the
> user/kernel access routines we could simplify that to an AND with an
> immediate mask to force all pointers into the user half of the address
> space. IIUC x86_64 could do the same, and I think that was roughly what
> David was suggesting.

True.  On 64-bit arches it might be as simple as just clearing the
most-significant bit.

-- 
Josh


  reply	other threads:[~2021-05-05 14:48 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
2021-05-06  7:57       ` David Laight
2021-05-05 14:25   ` Mark Rutland
2021-05-05 14:48     ` Josh Poimboeuf [this message]
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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