linux-kernel - Re: [PATCH 3.15] x86,vdso: Fix an OOPS accessing the hpet mapping w/o an hpet

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Message-Id: <20140514161630.d604884474d13a4432360b0f@linux-foundation.org>
Date:	Wed, 14 May 2014 16:16:30 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	x86@...nel.org, Sasha Levin <sasha.levin@...cle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Dave Jones <davej@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3.15] x86,vdso: Fix an OOPS accessing the hpet mapping
 w/o an hpet

On Wed, 14 May 2014 16:01:22 -0700 Andy Lutomirski <luto@...capital.net> wrote:

> The access should fail, but it shouldn't oops.
> 
> Signed-off-by: Andy Lutomirski <luto@...capital.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?

> --- 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().

>  /* 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);

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