From: Thomas Gleixner <tglx@linutronix.de>
To: "Frank Ch. Eigler" <fche@redhat.com>
Cc: David Smith <dsmith@redhat.com>,
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>
Subject: Re: [RFC][PATCH] x86: Verify access_ok() context
Date: Fri, 20 Jan 2017 00:04:17 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1701200000080.5358@nanos> (raw)
In-Reply-To: <20170119212718.GC20931@redhat.com>
Frank.
On Thu, 19 Jan 2017, Frank Ch. Eigler wrote:
> > Well, if you are not in thread context then the check is pointless:
> > __range_not_ok(addr, size, user_addr_max())
> > and:
> > #define user_addr_max() (current->thread.addr_limit.seg)
> >
> > So what guarantees when you are not in context of current, i.e. in thread
> > context, that the addr/size which is checked against the limits of current
> > actually belongs to current?
>
> We're probably in task context in that there is a valid current(), but
current is always accessible no matter in which context you are - task,
softirq, hardirq, nmi ...
> running with preemption and/or interrupts and/or pagefaults disabled
> at that point, so in_task() objects.
As Peter explained, neither preempt disable nor interrupt disable not
pagefault disabled have any influence on in_task(). It merily checks the
context: !in_softirq() && !in_hardirq() && !in_nmi().
So that warning happens definitely not from task context.
Care to share the code?
Thanks,
tglx
prev parent reply other threads:[~2017-01-19 23:44 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
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 [this message]
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