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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
	Luis Henriques <lhenriques@suse.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	Greg KH <gregkh@linuxfoundation.org>, X86 ML <x86@kernel.org>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alan Cox <alan@linux.intel.com>
Subject: Re: [PATCH v4 07/10] x86: narrow out of bounds syscalls to sys_read under speculation
Date: Tue, 6 Feb 2018 14:52:59 -0800	[thread overview]
Message-ID: <CA+55aFxU_vo+JFBZcvE5EOs2D_QHNXBf4G=-KT=3LeP2zjECHw@mail.gmail.com> (raw)
In-Reply-To: <CAPcyv4hELJQMEBQ_gi+_bh4D=7h47ypzK++XTdQjhDGnOs2uRg@mail.gmail.com>

On Tue, Feb 6, 2018 at 1:37 PM, Dan Williams <dan.j.williams@intel.com> wrote:
>
> At that point we're basically just back to the array_ptr() version
> that returned a sanitized pointer to an array element.

.. that one does an extra unnecessary 'andq' instead of the duplicated
cmp.  But at least it avoids comparing that 32-bit integer twice, so
it's probably slightly smaller.

(And your code generation is without the "r" -> "ir" fix for the size argument)

Probably doesn't matter. But a "asm goto" would give you at least
potentially optimal code.

            Linus

  reply	other threads:[~2018-02-06 22:52 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-19  0:01 [PATCH v4 00/10] prevent bounds-check bypass via speculative execution Dan Williams
2018-01-19  0:01 ` [kernel-hardening] " Dan Williams
2018-01-19  0:01 ` Dan Williams
2018-01-19  0:01 ` [PATCH v4 01/10] Documentation: document array_ptr Dan Williams
2018-01-19  0:01   ` [kernel-hardening] " Dan Williams
2018-01-19  0:01 ` [PATCH v4 02/10] asm/nospec, array_ptr: sanitize speculative array de-references Dan Williams
2018-01-19  0:01   ` [kernel-hardening] " Dan Williams
2018-01-19 10:20   ` Jann Horn
2018-01-19 17:48     ` Adam Sampson
2018-01-19 17:48       ` Adam Sampson
2018-01-19 17:48       ` Adam Sampson
2018-01-19 17:48       ` Adam Sampson
2018-01-19 18:12       ` Dan Williams
2018-01-19 18:18         ` Will Deacon
2018-01-19 18:18           ` Will Deacon
2018-01-19 18:26           ` [kernel-hardening] " Dan Williams
2018-01-19 18:18     ` Linus Torvalds
2018-01-19 18:18       ` Linus Torvalds
2018-01-19 20:55       ` [kernel-hardening] " Dan Williams
2018-01-25  7:09   ` Cyril Novikov
2018-01-25  7:09     ` [kernel-hardening] " Cyril Novikov
2018-01-25 22:37     ` Dan Williams
2018-01-25 22:37       ` [kernel-hardening] " Dan Williams
2018-01-19  0:01 ` [PATCH v4 03/10] x86: implement array_ptr_mask() Dan Williams
2018-01-19  0:01   ` [kernel-hardening] " Dan Williams
2018-01-19  0:01 ` [PATCH v4 04/10] x86: introduce __uaccess_begin_nospec and ifence Dan Williams
2018-01-19  0:01   ` [kernel-hardening] " Dan Williams
2018-01-19  0:02 ` [PATCH v4 05/10] x86, __get_user: use __uaccess_begin_nospec Dan Williams
2018-01-19  0:02   ` [kernel-hardening] " Dan Williams
2018-01-19  0:02 ` [PATCH v4 06/10] x86, get_user: use pointer masking to limit speculation Dan Williams
2018-01-19  0:02   ` [kernel-hardening] " Dan Williams
2018-01-19  0:02 ` [PATCH v4 07/10] x86: narrow out of bounds syscalls to sys_read under speculation Dan Williams
2018-01-19  0:02   ` [kernel-hardening] " Dan Williams
2018-01-24 14:40   ` Jiri Slaby
2018-01-24 14:40     ` [kernel-hardening] " Jiri Slaby
2018-02-06 19:29   ` Luis Henriques
2018-02-06 19:48     ` Dan Williams
2018-02-06 20:26       ` Linus Torvalds
2018-02-06 20:37         ` Dan Williams
2018-02-06 20:42           ` Linus Torvalds
2018-02-06 20:43             ` Linus Torvalds
2018-02-06 20:49             ` Andy Lutomirski
2018-02-06 20:58               ` Linus Torvalds
2018-02-06 21:37                 ` Dan Williams
2018-02-06 22:52                   ` Linus Torvalds [this message]
2018-02-07  0:33                     ` Dan Williams
2018-02-07  1:23                       ` Linus Torvalds
2018-02-06 22:51       ` Luis Henriques
2018-02-06 22:51         ` Luis Henriques
2018-01-19  0:02 ` [PATCH v4 08/10] vfs, fdtable: prevent bounds-check bypass via speculative execution Dan Williams
2018-01-19  0:02   ` [kernel-hardening] " Dan Williams
2018-01-19  0:02 ` [PATCH v4 09/10] kvm, x86: fix spectre-v1 mitigation Dan Williams
2018-01-19  0:02   ` [kernel-hardening] " Dan Williams
2018-01-19  8:42   ` Paolo Bonzini
2018-01-19  8:42     ` [kernel-hardening] " Paolo Bonzini
2018-01-19  0:02 ` [PATCH v4 10/10] nl80211: sanitize array index in parse_txq_params Dan Williams
2018-01-19  0:02   ` [kernel-hardening] " Dan Williams
2018-01-19  0:02   ` Dan Williams
2018-01-21 10:37   ` Johannes Berg
2018-01-21 10:37     ` [kernel-hardening] " Johannes Berg
2018-01-21 10:37     ` Johannes Berg
2018-01-20  6:58 ` [PATCH v4 00/10] prevent bounds-check bypass via speculative execution Dan Williams
2018-01-20  6:58   ` [kernel-hardening] " Dan Williams
2018-01-20  6:58   ` Dan Williams
2018-01-20 16:56   ` Alexei Starovoitov
2018-01-20 16:56     ` [kernel-hardening] " Alexei Starovoitov
2018-01-20 16:56     ` Alexei Starovoitov
2018-01-20 17:07     ` Alexei Starovoitov
2018-01-20 17:07       ` [kernel-hardening] " Alexei Starovoitov
2018-01-20 17:07       ` Alexei Starovoitov

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