From: Josh Poimboeuf <jpoimboe@kernel.org>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Peter Zijlstra <peterz@infradead.org>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Waiman Long <longman@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Michael Ellerman <mpe@ellerman.id.au>,
linuxppc-dev@lists.ozlabs.org,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH] x86/uaccess: Avoid barrier_nospec() in copy_from_user()
Date: Sat, 12 Oct 2024 09:09:23 -0500 [thread overview]
Message-ID: <20241012140923.kl2evqb6aue2pzfs@treble> (raw)
In-Reply-To: <f6ea59b1-eb59-4d1d-81ed-0e5095102c20@citrix.com>
On Sat, Oct 12, 2024 at 09:48:57AM +0100, Andrew Cooper wrote:
> On 12/10/2024 5:09 am, Josh Poimboeuf wrote:
> > For x86-64, the barrier_nospec() in copy_from_user() is overkill and
> > painfully slow. Instead, use pointer masking to force the user pointer
> > to a non-kernel value even in speculative paths.
> >
> > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
>
> You do realise mask_user_address() is unsafe under speculation on AMD
> systems?
>
> Had the mask_user_address() patch been put for review, this feedback
> would have been given then.
>
>
> AMD needs to arrange for bit 47 (bit 58 with LA57) to be the one
> saturated by shifting, not bit 63.
Ok... why?
--
Josh
next prev parent reply other threads:[~2024-10-12 14:09 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-12 4:09 [PATCH] x86/uaccess: Avoid barrier_nospec() in copy_from_user() Josh Poimboeuf
2024-10-12 8:48 ` Andrew Cooper
2024-10-12 14:09 ` Josh Poimboeuf [this message]
2024-10-12 14:21 ` Borislav Petkov
2024-10-12 15:58 ` Linus Torvalds
2024-10-12 14:26 ` Andrew Cooper
2024-10-12 15:44 ` Linus Torvalds
2024-10-12 17:23 ` Andrew Cooper
2024-10-12 17:44 ` Linus Torvalds
2024-10-13 0:53 ` Linus Torvalds
2024-10-13 1:21 ` Linus Torvalds
2024-10-14 3:54 ` Josh Poimboeuf
2024-10-14 6:50 ` Linus Torvalds
2024-10-14 9:59 ` David Laight
2024-10-14 11:20 ` Linus Torvalds
2024-10-14 14:40 ` David Laight
2024-10-14 11:12 ` Andrew Cooper
2024-10-14 12:30 ` Kirill A. Shutemov
2024-10-14 15:39 ` Andrew Cooper
2024-10-15 10:00 ` Borislav Petkov
2024-10-20 22:44 ` Josh Poimboeuf
2024-10-20 22:59 ` Linus Torvalds
2024-10-20 23:11 ` Josh Poimboeuf
2024-10-20 23:14 ` Josh Poimboeuf
2024-10-20 23:35 ` Linus Torvalds
2024-10-23 9:44 ` Borislav Petkov
2024-10-23 19:17 ` Linus Torvalds
2024-10-23 20:07 ` Linus Torvalds
2024-10-23 23:32 ` Linus Torvalds
2024-10-24 2:00 ` Linus Torvalds
2024-10-24 9:21 ` David Laight
2024-10-24 16:53 ` Linus Torvalds
2024-10-25 8:56 ` David Laight
2024-10-25 16:35 ` Linus Torvalds
2024-10-21 10:48 ` Kirill A. Shutemov
2024-10-22 2:36 ` Linus Torvalds
2024-10-22 10:33 ` Kirill A. Shutemov
2024-10-22 8:16 ` Pawan Gupta
2024-10-22 10:44 ` Kirill A. Shutemov
2024-10-14 16:55 ` Linus Torvalds
2024-10-16 16:10 ` Linus Torvalds
2024-10-16 22:02 ` Andrew Cooper
2024-10-16 22:13 ` Kirill A. Shutemov
2024-10-16 22:34 ` Linus Torvalds
2024-10-28 11:29 ` Kirill A. Shutemov
2024-10-28 18:44 ` Linus Torvalds
2024-10-28 20:31 ` Kirill A. Shutemov
2024-10-28 20:49 ` Linus Torvalds
2024-10-16 22:32 ` Linus Torvalds
2024-10-17 11:00 ` Borislav Petkov
2024-10-14 11:56 ` Kirill A. Shutemov
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