From: "Jan Beulich" <JBeulich@suse.com>
To: "Ingo Molnar" <mingo@kernel.org>
Cc: <mingo@elte.hu>, <tglx@linutronix.de>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Juergen Gross" <jgross@suse.com>, <linux-kernel@vger.kernel.org>,
<hpa@zytor.com>
Subject: Re: [PATCH v2] x86: consider effective protection attributes in W+X check
Date: Thu, 22 Feb 2018 03:13:17 -0700 [thread overview]
Message-ID: <5A8EA5CD02000078001AA4CA@prv-mh.provo.novell.com> (raw)
In-Reply-To: <20180221165344.ioxrxbsd6kkrhr2v@gmail.com>
>>> On 21.02.18 at 17:53, <mingo@kernel.org> wrote:
> * Jan Beulich <JBeulich@suse.com> wrote:
>
>> Using just the leaf page table entry flags would cause a false warning
>> in case _PAGE_RW is clear or _PAGE_NX is set in a higher level entry.
>> Hand through both the current entry's flags as well as the accumulated
>> effective value (the latter as pgprotval_t instead of pgprot_t, as it's
>> not an actual entry's value).
>>
>> This in particular eliminates the false W+X warning when running under
>> Xen, as commit 2cc42bac1c ("x86-64/Xen: eliminate W+X mappings") has to
>> make the necessary adjustment in L2 rather than L1 (the reason is
>> explained there). I.e. _PAGE_RW is clear there in L1, but _PAGE_NX is
>> set in L2.
>>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>> Reviewed-by: Juergen Gross <jgross@suse.com>
>> ---
>> v2: Re-base onto tip tree. Add Xen related paragraph to description.
>> ---
>> arch/x86/mm/dump_pagetables.c | 92
> ++++++++++++++++++++++++++----------------
>> 1 file changed, 57 insertions(+), 35 deletions(-)
>
> There's a build failure with CONFIG_KASAN=y enabled:
>
> arch/x86/mm/dump_pagetables.c: In function ‘kasan_page_table’:
> arch/x86/mm/dump_pagetables.c:365:3: error: too few arguments to function ‘note_page’
> arch/x86/mm/dump_pagetables.c:238:13: note: declared here
Oh, I see. Question though is what to pass as the extra argument:
Do I need to pass in the caller's effective rights, or should I take
kasan_page_table()'s checking against kasan_zero_p?d as an
indication that the effective permission is zero here? I'm sorry for
this probably trivial question, but I know nothing about how KASAN
works.
Jan
next prev parent reply other threads:[~2018-02-22 10:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-21 14:34 [PATCH v2] x86: consider effective protection attributes in W+X check Jan Beulich
2018-02-21 16:53 ` Ingo Molnar
2018-02-22 10:13 ` Jan Beulich [this message]
2018-02-23 7:49 ` Ingo Molnar
2018-02-23 7:57 ` Jan Beulich
2018-02-23 8:27 ` [PATCH v3] " Jan Beulich
2018-02-23 10:13 ` [tip:x86/mm] x86/mm: Consider " tip-bot for Jan Beulich
2018-02-26 8:48 ` tip-bot for Jan Beulich
2018-02-26 10:00 ` Andrey Ryabinin
2018-02-26 10:08 ` Jan Beulich
2018-02-26 10:47 ` Andrey Ryabinin
2018-02-26 10:54 ` Jan Beulich
2018-02-26 12:46 ` Andrey Ryabinin
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