From: Russell King <rmk+lkml@arm.linux.org.uk>
To: "Steven J. Magnani" <steve@digidescorp.com>
Cc: Joerg Roedel <joerg.roedel@amd.com>,
monstr@monstr.eu, linux-kernel@vger.kernel.org,
michal.simek@petalogix.com, arnd@arndb.de,
linux-arch@vger.kernel.org, fujita.tomonori@lab.ntt.co.jp,
akpm@linux-foundation.org, mingo@elte.hu
Subject: Re: Generic DMA - BUG_ON
Date: Thu, 21 Jan 2010 17:53:17 +0000 [thread overview]
Message-ID: <20100121175317.GA14752@flint.arm.linux.org.uk> (raw)
In-Reply-To: <1264089097.18869.0.camel@iscandar.digidescorp.com>
On Thu, Jan 21, 2010 at 09:51:37AM -0600, Steven J. Magnani wrote:
> On Wed, 2010-01-20 at 12:00 +0100, Joerg Roedel wrote:
> > On Wed, Jan 20, 2010 at 10:53:50AM +0000, Russell King wrote:
> > > and ops is NULL, then this code will oops; you will get a full register
> > > dump and backtrace. You can use this information along with markup_oops.pl
> > > to find out where the problem is.
> >
> > You can't rely on the oops if the code runs in process context. The
> > process may have address 0 mapped which would result in a security hole.
> > We had two of these bugs last year.
>
> You also can't rely on an oops in a NOMMU environment.
I don't see why implementations where NULL pointer derefs should be
penalized by having additional NULL checks.
Maybe this needs to be a conditional check which can be optimized away
on architectures where NULL dereference always produces an oops.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of:
prev parent reply other threads:[~2010-01-21 17:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-20 10:08 Generic DMA - BUG_ON monstr
2010-01-20 10:08 ` [PATCH] asm-generic: dma: Add BUG_ON for uninitialized dma_ops monstr
2010-01-20 10:48 ` Alexey Dobriyan
2010-01-20 11:00 ` Geert Uytterhoeven
2010-01-20 10:56 ` Joerg Roedel
2010-01-22 1:11 ` FUJITA Tomonori
2010-01-20 10:53 ` Generic DMA - BUG_ON Russell King
2010-01-20 11:00 ` Joerg Roedel
2010-01-20 11:18 ` Michal Simek
2010-01-20 19:03 ` Arnd Bergmann
2010-01-21 15:51 ` Steven J. Magnani
2010-01-21 17:53 ` Russell King [this message]
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