lkml.org 
[lkml]   [2018]   [Aug]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86/speculation/l1tf: fix overflow on l1tf_pfn_limit() on 32bit
On Mon 20-08-18 07:20:27, Andi Kleen wrote:
> On Mon, Aug 20, 2018 at 11:58:35AM +0200, Vlastimil Babka wrote:
> > On 32bit PAE kernels on 64bit hardware with enough physical bits,
> > l1tf_pfn_limit() will overflow unsigned long. This in turn affects
> > max_swapfile_size() and can lead to swapon returning -EINVAL. This has been
> > observed in a 32bit guest with 42 bits physical address size, where
> > max_swapfile_size() overflows exactly to 1 << 32, thus zero, and produces the
> > following warning to dmesg:
> >
> > [ 6.396845] Truncating oversized swap area, only using 0k out of 2047996k
> >
> > Fix this by using unsigned long long instead.
>
> Looks good.
>
> Acked-by: Andi Kleen <ak@linux.intel.com>
>
> BTW our much worse problems right now are crash reports on several
> stable kernels, especially with large pages

Do you have any reference?

> I'll dig into this more today, but if you have any hints from testing/fixing
> your own backports please share them.

Well, we have seen some issues on pre 3.12 kernels due to misbackporting
prot_none mitigations. PMD format is different in pre 4.4 kernels. Maybe
this is a similar issue.
--
Michal Hocko
SUSE Labs

\
 
 \ /
  Last update: 2018-08-20 16:27    [W:0.086 / U:0.296 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site