From: Julia Lawall <julia.lawall@lip6.fr>
To: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Alexandre Belloni <alexandre.belloni@free-electrons.com>,
Kees Cook <keescook@chromium.org>,
andrew@lunn.ch, Jason Cooper <jason@lakedaemon.net>,
rtc-linux@googlegroups.com, a.zummo@towertech.it,
LKML <linux-kernel@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
gregory.clement@free-electrons.com,
Bhumika Goyal <bhumirks@gmail.com>,
sebastian.hesselbarth@gmail.com
Subject: Re: [PATCH] rtc: armada38x: add __ro_after_init to armada38x_rtc_ops
Date: Wed, 4 Jan 2017 14:41:16 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1701041441020.3073@hadrien> (raw)
In-Reply-To: <20170104130628.GQ14217@n2100.armlinux.org.uk>
On Wed, 4 Jan 2017, Russell King - ARM Linux wrote:
> On Wed, Jan 04, 2017 at 01:23:41PM +0100, Julia Lawall wrote:
> > Basically, the strategy of the patch is that one may consider it
> > preferable to duplicate the structure for the different alternatives,
> > rather than use __ro_after_init. Perhaps if the structure were larger,
> > then __ro_after_init would be a better choice?
>
> It depends on not just the size, but how many members need to be
> modified, and obviously whether there are likely to be more than one
> user of the structure as well.
>
> So I'd say __ro_after_init rarely makes sense for an operations
> structure - the only case I can see is:
>
> - a large structure
> - only a small number of elements need to be modified
> - it is only single-use
>
> which is probably quite rare - this one falls into two out of those
> three.
>
> There's another consideration (imho) too - we may wish, at a later
> date, to make .text and .rodata both read-only from the start of the
> kernel to harden the kernel against possibly init-time exploitation.
> (Think about a buggy built-in driver with emulated hardware - much the
> same problem that Kees is trying to address in one of his recent patch
> sets but with hotplugged hardware while a screen-saver is active.)
> Having function pointers in .rodata rather than the ro-after-init
> section would provide better protection.
OK, thanks for the explanations.
julia
next prev parent reply other threads:[~2017-01-04 13:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-26 11:31 [PATCH] rtc: armada38x: add __ro_after_init to armada38x_rtc_ops Bhumika Goyal
2017-01-02 14:06 ` Russell King - ARM Linux
2017-01-03 21:18 ` Kees Cook
2017-01-03 21:31 ` Russell King - ARM Linux
2017-01-03 21:54 ` Russell King - ARM Linux
2017-01-04 10:57 ` Julia Lawall
2017-01-04 11:07 ` Alexandre Belloni
2017-01-04 11:43 ` Julia Lawall
2017-01-04 12:14 ` Russell King - ARM Linux
2017-01-04 12:23 ` Julia Lawall
2017-01-04 13:06 ` Russell King - ARM Linux
2017-01-04 13:41 ` Julia Lawall [this message]
2017-01-04 21:53 ` Kees Cook
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