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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Richard Henderson <rth@twiddle.net>,
	Will Deacon <will.deacon@arm.com>,
	Haavard Skinnemoen <hskinnemoen@gmail.com>,
	Vineet Gupta <vgupta@synopsys.com>,
	Steven Miao <realmz6@gmail.com>,
	Jesper Nilsson <jesper.nilsson@axis.com>,
	Mark Salter <msalter@redhat.com>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Richard Kuo <rkuo@codeaurora.org>,
	Tony Luck <tony.luck@intel.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	James Hogan <james.hogan@imgtec.com>,
	Michal Simek <monstr@monstr.eu>,
	David Howells <dhowells@redhat.com>,
	Ley Foon Tan <lftan@altera.com>, Jonas Bonn <jonas@southpole.se>,
	Helge Deller <deller@gmx.de>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Ralf Baechle <ralf@linux-mips.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Chen Liqin <liqin.linux@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Chris Metcalf <cmetcalf@mellanox.com>,
	Richard Weinberger <richard@nod.at>,
	Guan Xuetao <gxt@mprc.pku.edu.cn>,
	Thomas Gleixner <tglx@linutronix.de>,
	Chris Zankel <chris@zankel.net>
Subject: Re: [RFC][CFT][PATCHSET v1] uaccess unification
Date: Thu, 30 Mar 2017 20:10:09 +0100	[thread overview]
Message-ID: <20170330191009.GU29622@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFx2u6iUzJV1ZH4w_o6tTZesSGoOxMrOtJB8aXScou6zPg@mail.gmail.com>

On Thu, Mar 30, 2017 at 11:59:16AM -0700, Linus Torvalds wrote:

> But regardless of that, I think you're being silly to even look at the
> iovec code. That code simply *isn't* critical enough that one or two
> extra instructions matter.
> 
> Show me profiles to the contrary. I dare you.
> 
> Those things shouldn't be using *anything* odd at all. They should be
> using "copy_from_user()". Nothing else.

That they very definitely should not.  And not because of access_ok() or
might_fault() - this is one place where zero-padding is absolutely wrong.
So unless you are going to take it out of copy_from_user() and pray
that random shit ioctls in random shit drivers check the return value
properly, copy_from_user() is no-go here.

WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Richard Henderson <rth@twiddle.net>,
	Will Deacon <will.deacon@arm.com>,
	Haavard Skinnemoen <hskinnemoen@gmail.com>,
	Vineet Gupta <vgupta@synopsys.com>,
	Steven Miao <realmz6@gmail.com>,
	Jesper Nilsson <jesper.nilsson@axis.com>,
	Mark Salter <msalter@redhat.com>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Richard Kuo <rkuo@codeaurora.org>,
	Tony Luck <tony.luck@intel.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	James Hogan <james.hogan@imgtec.com>,
	Michal Simek <monstr@monstr.eu>,
	David Howells <dhowells@redhat.com>,
	Ley Foon Tan <lftan@altera.com>, Jonas Bonn <jonas@southpole>
Subject: Re: [RFC][CFT][PATCHSET v1] uaccess unification
Date: Thu, 30 Mar 2017 20:10:09 +0100	[thread overview]
Message-ID: <20170330191009.GU29622@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFx2u6iUzJV1ZH4w_o6tTZesSGoOxMrOtJB8aXScou6zPg@mail.gmail.com>

On Thu, Mar 30, 2017 at 11:59:16AM -0700, Linus Torvalds wrote:

> But regardless of that, I think you're being silly to even look at the
> iovec code. That code simply *isn't* critical enough that one or two
> extra instructions matter.
> 
> Show me profiles to the contrary. I dare you.
> 
> Those things shouldn't be using *anything* odd at all. They should be
> using "copy_from_user()". Nothing else.

That they very definitely should not.  And not because of access_ok() or
might_fault() - this is one place where zero-padding is absolutely wrong.
So unless you are going to take it out of copy_from_user() and pray
that random shit ioctls in random shit drivers check the return value
properly, copy_from_user() is no-go here.

  reply	other threads:[~2017-03-30 19:10 UTC|newest]

Thread overview: 83+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-29  5:57 [RFC][CFT][PATCHSET v1] uaccess unification Al Viro
2017-03-29  5:57 ` Al Viro
2017-03-29 20:08 ` Vineet Gupta
2017-03-29 20:08   ` Vineet Gupta
2017-03-29 20:08   ` Vineet Gupta
2017-03-29 20:29   ` Al Viro
2017-03-29 20:29     ` Al Viro
2017-03-29 20:37     ` Linus Torvalds
2017-03-29 20:37       ` Linus Torvalds
2017-03-29 21:03       ` Al Viro
2017-03-29 21:03         ` Al Viro
2017-03-29 21:24         ` Linus Torvalds
2017-03-29 21:24           ` Linus Torvalds
2017-03-29 23:09           ` Al Viro
2017-03-29 23:09             ` Al Viro
2017-03-29 23:43             ` Linus Torvalds
2017-03-29 23:43               ` Linus Torvalds
2017-03-30 15:31               ` Al Viro
2017-03-30 15:31                 ` Al Viro
2017-03-29 21:14     ` Vineet Gupta
2017-03-29 21:14       ` Vineet Gupta
2017-03-29 23:42       ` Al Viro
2017-03-29 23:42         ` Al Viro
2017-03-30  0:02         ` Vineet Gupta
2017-03-30  0:02           ` Vineet Gupta
2017-03-30  0:27           ` Linus Torvalds
2017-03-30  0:27             ` Linus Torvalds
2017-03-30  1:15             ` Al Viro
2017-03-30  1:15               ` Al Viro
2017-03-30 20:40             ` Vineet Gupta
2017-03-30 20:40               ` Vineet Gupta
2017-03-30 20:59               ` Linus Torvalds
2017-03-30 20:59                 ` Linus Torvalds
2017-03-30 23:21                 ` Russell King - ARM Linux
2017-03-30 23:21                   ` Russell King - ARM Linux
2017-03-30 12:32 ` Martin Schwidefsky
2017-03-30 12:32   ` Martin Schwidefsky
2017-03-30 14:48   ` Al Viro
2017-03-30 14:48     ` Al Viro
2017-03-30 16:22 ` Russell King - ARM Linux
2017-03-30 16:22   ` Russell King - ARM Linux
2017-03-30 16:43   ` Al Viro
2017-03-30 16:43     ` Al Viro
2017-03-30 17:18     ` Linus Torvalds
2017-03-30 17:18       ` Linus Torvalds
2017-03-30 18:48       ` Al Viro
2017-03-30 18:48         ` Al Viro
2017-03-30 18:54         ` Al Viro
2017-03-30 18:54           ` Al Viro
2017-03-30 18:59           ` Linus Torvalds
2017-03-30 18:59             ` Linus Torvalds
2017-03-30 19:10             ` Al Viro [this message]
2017-03-30 19:10               ` Al Viro
2017-03-30 19:19               ` Linus Torvalds
2017-03-30 19:19                 ` Linus Torvalds
2017-03-30 21:08                 ` Al Viro
2017-03-30 21:08                   ` Al Viro
2017-03-30 18:56         ` Linus Torvalds
2017-03-30 18:56           ` Linus Torvalds
2017-03-31  0:21 ` Kees Cook
2017-03-31  0:21   ` Kees Cook
2017-03-31 13:38   ` James Hogan
2017-03-31 13:38     ` James Hogan
2017-04-03 16:27 ` James Morse
2017-04-03 16:27   ` James Morse
2017-04-04 20:26 ` Max Filippov
2017-04-04 20:26   ` Max Filippov
2017-04-04 20:26   ` Max Filippov
2017-04-04 20:52   ` Al Viro
2017-04-04 20:52     ` Al Viro
2017-04-05  5:05 ` ia64 exceptions (Re: [RFC][CFT][PATCHSET v1] uaccess unification) Al Viro
2017-04-05  5:05   ` Al Viro
2017-04-05  8:08   ` Al Viro
2017-04-05  8:08     ` Al Viro
2017-04-05 18:44     ` Tony Luck
2017-04-05 18:44       ` Tony Luck
2017-04-05 20:33       ` Al Viro
2017-04-05 20:33         ` Al Viro
2017-04-07  0:24 ` [RFC][CFT][PATCHSET v2] uaccess unification Al Viro
2017-04-07  0:24   ` Al Viro
2017-04-07  0:35   ` Al Viro
2017-04-07  0:35     ` Al Viro
     [not found] <CACVxJT8+fQqvpSPb9rTWFy6g7moqUqxi+Ewjcg0ykuqo=vm4Ow@mail.gmail.com>
2017-03-30 13:27 ` [RFC][CFT][PATCHSET v1] " Alexey Dobriyan

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