From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 5/5] arm: Enable IRQs before attempting to read user space in __und_usr
Date: Thu, 21 Nov 2013 10:29:23 +0000 [thread overview]
Message-ID: <20131121102923.GV16735@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <loom.20131121T102616-386@post.gmane.org>
On Thu, Nov 21, 2013 at 09:35:34AM +0000, Alexey Ignatov wrote:
> Catalin Marinas <catalin.marinas <at> arm.com> writes:
>
> > The Undef abort handler in the kernel reads the undefined instruction
> > from user space. If the page table was modified from another CPU, the
> > user access could fail and do_page_fault() will be executed with
> > interrupts disabled. This can potentially deadlock on ARM11MPCore or on
> > Cortex-A15 with erratum 798181 workaround enabled (both implying IPI for
> > TLB maintenance with page table lock held).
> >
> > This patch enables the IRQs in __und_usr before attempting to read the
> > instruction from user space.
>
> This patch moves enable_irq call from do_fpe directly to __und_usr handler,
> but __und_svc handler also calls do_fpe (via call_fpe), so now this codepath
> runs with disabled irqs. This behavior change doesn't look good for me.
However, you're not executing FPA instructions in the kernel as a general
rule, so it doesn't matter.
next prev parent reply other threads:[~2013-11-21 10:29 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-28 11:34 [PATCH 0/5] arm: Early IRQ enabling in the Undef user handler Catalin Marinas
2013-08-28 11:34 ` [PATCH 1/5] arm: Move asm macro get_thread_info to asm/assembler.h Catalin Marinas
2013-08-28 11:34 ` [PATCH 2/5] arm: Add {inc,dec}_preempt_count asm macros Catalin Marinas
2013-08-28 11:34 ` [PATCH 3/5] arm: Disable preemption in iwmmxt_task_enable() Catalin Marinas
2013-08-28 11:34 ` [PATCH 4/5] arm: Disable preemption in crunch_task_enable() Catalin Marinas
2013-08-28 11:34 ` [PATCH 5/5] arm: Enable IRQs before attempting to read user space in __und_usr Catalin Marinas
2013-11-21 9:35 ` Alexey Ignatov
2013-11-21 10:29 ` Russell King - ARM Linux [this message]
2013-11-22 9:47 ` Alexey Ignatov
2014-03-31 4:11 ` [PATCH 0/5] arm: Early IRQ enabling in the Undef user handler Yang Zhang
-- strict thread matches above, loose matches on Subject: below --
2014-03-13 18:15 Catalin Marinas
2014-03-13 18:15 ` [PATCH 5/5] arm: Enable IRQs before attempting to read user space in __und_usr Catalin Marinas
2014-04-01 12:24 ` Arun KS
2014-04-01 14:48 ` Russell King - ARM Linux
2014-04-04 11:29 ` Arun KS
2014-04-04 15:42 ` Catalin Marinas
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