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From: Andy Lutomirski <luto@amacapital.net>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: x86@kernel.org, Ingo Molnar <mingo@elte.hu>,
	richard -rw- weinberger <richard.weinberger@gmail.com>,
	Adrian Bunk <bunk@stusta.de>,
	"H. Peter Anvin" <hpa@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org,
	Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH 0/2] Fix and re-enable vsyscall=emulate
Date: Fri, 2 Dec 2011 14:47:35 -0800	[thread overview]
Message-ID: <CALCETrVxHvH61D-xY6vq4ymWXAVOdj8=XV_ENqLQUJ5rMieuEg@mail.gmail.com> (raw)
In-Reply-To: <cover.1320712291.git.luto@amacapital.net>

On Mon, Nov 7, 2011 at 4:33 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> The really nice fix (wiring up access_ok failures to be able to raise
> signals) won't be ready on time for 3.2, so let's try the simpler fix
> for now.

I spoke to hpa about this a couple days ago, and he pointed out a
problem with making access_ok send signals.  Userspace expects signals
that come with full context information to be restartable, and many
system calls are not restartable.  read() and write() are the obvious
examples: once they're processed the beginning of the buffer, unless
they adjust their parameters, they can't safely be restarted.  So
without massive changes, I think allowing access_ok to raise a signal
with full context is asking for trouble.

I can still do the patch with two modes: signals without context via
arch_prctl and signals with context via vsyscall emulation, but that's
probably overkill for fixing this bug.  I'd say just apply these
patches as is (for 3.3).

--Andy

  parent reply	other threads:[~2011-12-02 22:47 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-10-03  9:08 [3.1 patch] x86: default to vsyscall=native Adrian Bunk
2011-10-03 13:04 ` Andrew Lutomirski
2011-10-03 17:33   ` Adrian Bunk
2011-10-03 18:06     ` Andrew Lutomirski
2011-10-03 18:41       ` Adrian Bunk
2011-10-05 22:13     ` Andrew Lutomirski
2011-10-05 22:22       ` richard -rw- weinberger
2011-10-05 22:30         ` Adrian Bunk
2011-10-05 22:41           ` richard -rw- weinberger
2011-10-05 22:46           ` Andrew Lutomirski
2011-10-05 23:36             ` Andrew Lutomirski
2011-10-06  3:06               ` Andrew Lutomirski
2011-10-06 12:12                 ` richard -rw- weinberger
2011-10-06 15:37                 ` richard -rw- weinberger
2011-10-06 18:16                   ` Andrew Lutomirski
2011-10-06 18:34                     ` Linus Torvalds
2011-10-07  0:48                       ` Andrew Lutomirski
2011-10-10 11:19                         ` richard -rw- weinberger
2011-10-10 11:48                           ` Ingo Molnar
2011-10-10 15:31                             ` Andrew Lutomirski
2011-10-11  6:22                               ` Ingo Molnar
2011-10-11 17:24                                 ` [RFC] fixing the UML failure root cause Andrew Lutomirski
2011-10-13  6:19                                   ` Linus Torvalds
2011-10-13  8:40                                     ` Andrew Lutomirski
2011-10-14  4:46                                       ` Linus Torvalds
2011-10-14  6:30                                         ` Andrew Lutomirski
2011-10-14 20:10                                           ` Linus Torvalds
2011-10-21 21:01                                             ` [PATCH] x86-64: Set siginfo and context on vsyscall emulation faults Andy Lutomirski
2011-10-22  4:46                                               ` Linus Torvalds
2011-10-22  9:07                                                 ` Andy Lutomirski
2011-11-08  0:33                                                   ` [PATCH 0/2] Fix and re-enable vsyscall=emulate Andy Lutomirski
2011-11-08  0:33                                                     ` [PATCH 1/2] x86-64: Set siginfo and context on vsyscall emulation faults Andy Lutomirski
2011-12-05 13:23                                                       ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2011-11-08  0:33                                                     ` [PATCH 2/2] x86: Default to vsyscall=emulate Andy Lutomirski
2011-12-05 13:24                                                       ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2011-12-02 22:47                                                     ` Andy Lutomirski [this message]
2011-12-05 11:18                                                       ` [PATCH 0/2] Fix and re-enable vsyscall=emulate H. Peter Anvin
2011-10-14 19:53                                   ` [RFC] fixing the UML failure root cause richard -rw- weinberger
2011-10-14 20:17                                     ` Andrew Lutomirski
2011-10-14 20:23                                       ` richard -rw- weinberger
2011-10-14 20:31                                         ` Andrew Lutomirski
2011-10-14 20:39                                           ` richard -rw- weinberger
2011-10-14 22:28                                       ` richard -rw- weinberger
2011-10-15 16:57                                         ` Ingo Molnar
2011-10-05 22:24       ` [3.1 patch] x86: default to vsyscall=native Adrian Bunk
2011-10-03 13:19 ` richard -rw- weinberger
2011-10-03 17:46   ` Adrian Bunk

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