From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
kirill.shutemov@linux.intel.com, shuah@kernel.org,
linux-kselftest@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH 1/2] x86, pkeys: check against max pkey to avoid overflows
Date: Fri, 24 Feb 2017 03:07:21 +0300 [thread overview]
Message-ID: <20170224000721.GA26920@node.shutemov.name> (raw)
In-Reply-To: <20170223222603.A022ED65@viggo.jf.intel.com>
On Thu, Feb 23, 2017 at 02:26:03PM -0800, Dave Hansen wrote:
>
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> Kirill got a warning from UBSAN about undefined behavior when using
> protection keys. He is running on hardware that actually has support
> for it, which is not widely available.
>
> The warning was because we did some very large shifts of integers when
> doing a pkey_free() of a large, invalid value because we never check
> that the pkey "fits" into the mm_pkey_allocation_map().
>
> I do not believe there is any danger here of anything bad happening
> other than some aliasing issues where somebody could do:
>
> pkey_free(35);
>
> and the kernel would effectively execute:
>
> pkey_free(8);
>
> While this might be confusing to an app that was doing something
> stupid, it has to do something stupid and the effects are limited to
> the app shooting itself in the foot.
>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
--
Kirill A. Shutemov
prev parent reply other threads:[~2017-02-24 0:08 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-23 22:26 [PATCH 1/2] x86, pkeys: check against max pkey to avoid overflows Dave Hansen
2017-02-24 0:07 ` Kirill A. Shutemov [this message]
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