linux-kernel - Re: mm/sched/net: BUG when running simple code

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Date:	Fri, 13 Jun 2014 08:26:30 +0300
From:	Dan Aloni <dan@...nelim.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: mm/sched/net: BUG when running simple code

On Fri, Jun 13, 2014 at 07:55:55AM +0300, Dan Aloni wrote:
> > that theory went away. (also confirmed by not finding a netlink module.)
> > 
> > What about the kernel .text overflowing into the modules space? The loader
> > checks for that, but can something like that happen after everything is
> > up and running? I'll look into that tomorrow.
> 
> The kernel .text needs to be more than 512MB for the overlap to happen. 
> 
>     ffffffff80000000 - ffffffffa0000000 (=512 MB)  kernel text mapping, from phys 0
> 
> Also, it is bizarre that symbol resolution resolved ffffffffa0f12560 to 
> a symbol that is in module space where af_netlink.o is surely not because of 
> "obj-y := af_netlink.o" in the Makefile. 
> 
> What does your /proc/kallsyms show when sorted with regards to the symbols
> in question?
> 
> Also curious are the addresses you have on the stack:
> 
> > [  516.309720] Stack:
> > [  516.309720]  ffff8803fc85ff18 ffff8803fc85ff18 ffff8803fc85fef8 8900200549908020
> > [  516.309720]  ffff8803fc85ff18 ffffffff9ff66470 ffff8803fc85ff18 0000000000000037
> > [  516.309720]  ffff8803fc85ff78 ffffffff9ff69d26 0000000000000037 0000000000000004
>[..]

Oh, just figured about the new kASLR feature that got enabled
recently, it explains the addresses, but there was supposed to be a
line for it in the Oops, so I'm puzzled.

-- 
Dan Aloni
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