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In-Reply-To: <20140514161630.d604884474d13a4432360b0f@linux-foundation.org>
References: <e1640272803e7711d9a43d9454dbdae57ba22eed.1400108299.git.luto@amacapital.net>
 <20140514161630.d604884474d13a4432360b0f@linux-foundation.org>
From: Andy Lutomirski <luto@amacapital.net>
Date: Wed, 14 May 2014 16:18:01 -0700
Message-ID: <CALCETrVEGs4_71su4PKhuJ+SRW0ecp6BkKzq6KOb1+bdCxgfTQ@mail.gmail.com>
Subject: Re: [PATCH 3.15] x86,vdso: Fix an OOPS accessing the hpet mapping w/o
 an hpet
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Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: X86 ML <x86@kernel.org>, Sasha Levin <sasha.levin@oracle.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Dave Jones <davej@redhat.com>, LKML <linux-kernel@vger.kernel.org>

On Wed, May 14, 2014 at 4:16 PM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Wed, 14 May 2014 16:01:22 -0700 Andy Lutomirski <luto@amacapital.net> wrote:
>
>> The access should fail, but it shouldn't oops.
>>
>> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
>> ---
>>
>> The oops can be triggered in qemu using -no-hpet (but not nohpet) by
>> running a 32-bit program and reading a couple of pages before the vdso.
>
> This sentence is the best part of the changelog!  People often do this
> - they put all the good stuff after the ^---.  I always move it into
> the changelog.
>
> So how old is this bug?

New in 3.15.

>
>> --- a/arch/x86/vdso/vdso32-setup.c
>> +++ b/arch/x86/vdso/vdso32-setup.c
>> @@ -147,6 +147,8 @@ int __init sysenter_setup(void)
>>       return 0;
>>  }
>>
>> +static struct page *no_pages[] = {NULL};
>
> nit: this could be local to arch_setup_additional_pages().

Will do.

>
>>  /* Setup a VMA at program startup for the vsyscall page */
>>  int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
>>  {
>> @@ -192,7 +194,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
>>                       addr -  VDSO_OFFSET(VDSO_PREV_PAGES),
>>                       VDSO_OFFSET(VDSO_PREV_PAGES),
>>                       VM_READ,
>> -                     NULL);
>> +                     no_pages);
>>
>>       if (IS_ERR(vma)) {
>>               ret = PTR_ERR(vma);
>

--Andy

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