linux-kernel - Re: [PATCH] PREEMPT_RT_FULL: arm coredump fails for cpu >= 4

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1317214993.24040.16.camel@twins>
Date:	Wed, 28 Sep 2011 15:03:13 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	frank.rowand@...sony.com
Cc:	"tglx@...utronix.de" <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PREEMPT_RT_FULL: arm coredump fails for cpu >= 4

On Tue, 2011-09-27 at 20:02 -0700, Frank Rowand wrote:
> 
> ARM can not use SPLIT_PTLOCK_CPUS if PREEMPT_RT_FULL because
> vectors_user_mapping() creates a VM_ALWAYSDUMP mapping of the vector page,
> but no ptl->lock has been allocated for the page.  An attempt to coredump
> that page will result in a kernel NULL pointer dereference when
> follow_page() attempts to lock the page.


> 
> This patch is needed only if mm-shrink-the-page-frame-to-rt-size.patch is
> applied. 

Yeah, vile hackery that is.. why isn't pgtable_page_ctor() called on
those pages?

Not that I care too much about split_pte_lock on ARM, they're mostly all
tiny machines anyway so the gain is marginal, but it would be good to
find out why the pgtable constructor isn't called properly.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/