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Date: Fri, 22 Jul 2016 00:43:12 -0400
From: Valdis.Kletnieks@...edu
To: kernel-hardening@...ts.openwall.com
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
Borislav Petkov <bp@...en8.de>, Nadav Amit <nadav.amit@...il.com>,
Kees Cook <keescook@...omium.org>, Brian Gerst <brgerst@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Josh Poimboeuf <jpoimboe@...hat.com>, Jann Horn <jann@...jh.net>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v5 03/32] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated
On Mon, 11 Jul 2016 13:53:36 -0700, Andy Lutomirski said:
> This avoids pointless races in which another CPU or task might see a
> partially populated global pgd entry. These races should normally
> be harmless, but, if another CPU propagates the entry via
> vmalloc_fault and then populate_pgd fails (due to memory allocation
> failure, for example), this prevents a use-after-free of the pgd
> entry.
>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> ---
> arch/x86/mm/pageattr.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
I just bisected a failure to boot down to this patch. On my Dell Latitude
laptop, it results in the kernel being loaded and then just basically sitting
there dead in the water - as far as I can tell, it dies before the kernel
ever gets going far enough to do any console I/O (even with ignore_loglevel).
Nothing in /sys/fs/pstore either. I admit not understanding the VM code
at all, so I don't have a clue *why* this causes indigestion...
CPU is an Intel Core i5-3340M in case that matters....
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