Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 21 Jul 2016 22:34:33 -0700
From: Andy Lutomirski <>
 Borislav Petkov <>, Nadav Amit <>,
 Kees Cook <>, Brian Gerst <>,
 Linus Torvalds <>,
 Josh Poimboeuf <>, Jann Horn <>,
 Heiko Carstens <>
Subject: Re: [PATCH v5 03/32] x86/cpa: In populate_pgd,
 don't set the pgd entry until it's populated

On 07/21/2016 09:43 PM, wrote:
> 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 <>
>> ---
>>  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....

How much memory do you have and what's your config?  My code is 
obviously buggy, but I'm wondering why neither I nor the 0day bot caught 

The attached patch is compile-tested only.  (Even Thunderbird doesn't 
want to send non-flowed text right now, sigh.)


View attachment "0001-x86-mm-Fix-populate_pgd.patch" of type "text/x-patch" (3464 bytes)

Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.