linux-kernel - Re: [PATCH urgent] x86: Save cr4 to mmu_cr4

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]

Date:	Fri, 1 Apr 2011 12:30:25 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...e.de>,
	"lkml20101129@...ton.leun.net" <lkml20101129@...ton.leun.net>
Subject: Re: [PATCH urgent] x86: Save cr4 to mmu_cr4_features at boot time

On Fri, 1 Apr 2011, Ingo Molnar wrote:
> 
> * Stefano Stabellini <stefano.stabellini@...citrix.com> wrote:
> 
> > Save cr4 to mmu_cr4_features at boot time
> > 
> > This patch fixes a freeze when resuming from hibernation, introduced by
> > "x86: Cleanup highmap after brk is concluded", commit id
> > e5f15b45ddf3afa2bbbb10c7ea34fb32b6de0a0e.
> > This patch should be backported to all the stable tree where the
> > offending commit is present.
> 
> No, the offending commit should be reverted from -stable. It's not at all clear 
> yet why this fix patch helps.

e5f15b45ddf3afa2bbbb10c7ea34fb32b6de0a0e removes cleanup_highmap_brk_end
because the initial mapping of the region between _brk_end and _end is
going to be cleared by cleanup_highmap instead.

However cleanup_highmap_brk_end was not only clearing mappings, it was
also setting mmu_cr4_features, and this bit was lost with the removal of
cleanup_highmap_brk_end.

So this fix patch restores things back to how they were before
e5f15b45ddf3afa2bbbb10c7ea34fb32b6de0a0e (apart from the fact that
mappings between _brk_end and _end are cleared in cleanup_highmap now).

Obviously settings mmu_cr4_features shouldn't have been done in
cleanup_highmap_brk_end, since it doesn't have anything to do with
mappings.

P.S.
I asked for a backport of e5f15b45ddf3afa2bbbb10c7ea34fb32b6de0a0e to
the stable trees because I forgot to add "CC stable@...nel.org" to the
commit message and this commit is needed to fix a critical crash on boot
on xen.
--
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/