From: David Smith <dsmith@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@amacapital.net>,
Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Frank Ch. Eigler" <fche@redhat.com>
Subject: Re: [RFC][PATCH] x86: Verify access_ok() context
Date: Wed, 18 Jan 2017 16:16:43 -0600 [thread overview]
Message-ID: <8758e5b4-050d-a5dd-2e58-e4f9dccc734b@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1701162211570.3923@nanos>
On 01/16/2017 03:14 PM, Thomas Gleixner wrote:
> On Mon, 16 Jan 2017, David Smith wrote:
>
>> If you call access_ok() with page faulting disabled, you'll still see
>> this new warning.
>
> And how so? It's just checking for task context. page fault disable/enable
> has absolutely nothing to do with that.
True, task context and page fault disable/enable have nothing to do with each other. However, the access_ok() comment states:
* Context: User context only. This function may sleep if pagefaults are
* enabled.
That seems to indicate that the function won't sleep if pagefaults are disabled, and thus there is no need for a CONFIG_DEBUG_ATOMIC_SLEEP warning if pagefaults are disabled.
>> If you put that new access_ok() call in a module that gets
>> loaded/unloaded, you see one warning for every module load, which gets a
>> bit annoying.
>
> Can you please elaborate where this access_ok() is placed in the module
> code?
It doesn't really matter where you place the access_ok() call in the module code. If you call access_ok() in a module, then that module has its own WARN_ON_ONCE() static variable. If access_ok() was a function exported from the kernel, then there would be only one copy of the WARN_ON_ONCE() static variable.
--
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)
next prev parent reply other threads:[~2017-01-18 22:16 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-22 9:57 [RFC][PATCH] x86: Verify access_ok() context Peter Zijlstra
2016-11-22 17:28 ` Andy Lutomirski
2016-11-22 19:37 ` Peter Zijlstra
2016-11-22 19:42 ` Linus Torvalds
2016-12-05 10:27 ` Peter Zijlstra
2017-01-16 20:27 ` David Smith
2017-01-16 21:14 ` Thomas Gleixner
2017-01-18 22:16 ` David Smith [this message]
2017-01-19 0:19 ` Andy Lutomirski
2017-01-19 15:37 ` David Smith
2017-01-20 8:24 ` Peter Zijlstra
2017-01-20 8:50 ` Thomas Gleixner
2017-01-19 18:12 ` Thomas Gleixner
2017-01-19 20:22 ` Frank Ch. Eigler
2017-01-19 20:50 ` Thomas Gleixner
2017-01-19 21:27 ` Frank Ch. Eigler
2017-01-19 22:20 ` Peter Zijlstra
2017-01-19 23:04 ` Thomas Gleixner
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