From: Michal Hocko <mhocko@kernel.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Dave Hansen <dave.hansen@intel.com>,
stable@vger.kernel.org, Adrian Schroeter <adrian@suse.de>,
Dominique Leuenberger <dimstar@suse.de>
Subject: Re: [PATCH] x86/speculation/l1tf: fix overflow on l1tf_pfn_limit() on 32bit
Date: Mon, 20 Aug 2018 16:26:36 +0200 [thread overview]
Message-ID: <20180820142636.GM29735@dhcp22.suse.cz> (raw)
In-Reply-To: <20180820142027.GL12066@tassilo.jf.intel.com>
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
next prev parent reply other threads:[~2018-08-20 14:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-20 9:58 [PATCH] x86/speculation/l1tf: fix overflow on l1tf_pfn_limit() on 32bit Vlastimil Babka
2018-08-20 10:49 ` Michal Hocko
2018-08-20 11:41 ` Vlastimil Babka
2018-08-20 14:27 ` Michal Hocko
2018-08-20 14:20 ` Andi Kleen
2018-08-20 14:26 ` Michal Hocko [this message]
2018-08-20 15:42 ` Andi Kleen
2018-08-20 16:11 ` [tip:x86/urgent] x86/speculation/l1tf: Fix overflow in " tip-bot for Vlastimil Babka
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