From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Lvqiang <Lvqiang.Huang@unisoc.com>
Cc: f.fainelli@gmail.com, anshuman.khandual@arm.com,
dave.hansen@linux.intel.com, linux-kernel@vger.kernel.org,
ebiederm@xmission.com, akpm@linux-foundation.org,
will@kernel.org, tglx@linutronix.de,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] ARM: check __ex_table in do_bad()
Date: Thu, 7 Nov 2019 09:24:04 +0000 [thread overview]
Message-ID: <20191107092404.GV25745@shell.armlinux.org.uk> (raw)
In-Reply-To: <1573112713-10115-1-git-send-email-Lvqiang.Huang@unisoc.com>
On Thu, Nov 07, 2019 at 03:45:13PM +0800, Lvqiang wrote:
>
> We got many crashs in for_each_frame+0x18 arch/arm/lib/backtrace.S
> 1003: ldr r2, [sv_pc, #-4]
>
> The backtrace is
> dump_backtrace
> show_stack
> sched_show_task
> show_state_filter
> sysrq_handle_showstate_blocked
> __handle_sysrq
> write_sysrq_trigger
> proc_reg_write
> __vfs_write
> vfs_write
> sys_write
>
> Related Kernel config
> CONFIG_CPU_SW_DOMAIN_PAN=y
> # CONFIG_ARM_UNWIND is not set
> CONFIG_FRAME_POINTER=y
>
> The task A was dumping the stack of an UN task B. However, the task B
What is "an UN task B"?
> scheduled to run on another CPU, which cause it stack content changed.
> Then, task A may hit a page domain fault and die().
> [520.661314] Unhandled fault: page domain fault (0x01b) at 0x32848c02
So, the backtrace code is trying to access userspace. It isn't supposed
to be accessing userspace - there are no guarantees that userspace will
be using frame pointers. That is the bug.
--
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next prev parent reply other threads:[~2019-11-07 9:25 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-07 7:45 [PATCH] ARM: check __ex_table in do_bad() Lvqiang
2019-11-07 9:24 ` Russell King - ARM Linux admin [this message]
2019-11-07 15:30 ` 黄吕强 (Lvqiang Huang)
2019-11-07 17:22 ` 黄吕强 (Lvqiang Huang)
2019-11-08 2:16 ` 黄吕强 (Lvqiang Huang)
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