linux-kernel - Re: [REVIEW][PATCH 16/20] signal/x86: Pass pkey not vma into __bad

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Date:   Tue, 18 Sep 2018 22:48:14 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
cc:     LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [REVIEW][PATCH 16/20] signal/x86: Pass pkey not vma into
 __bad_area

On Tue, 18 Sep 2018, Eric W. Biederman wrote:

> There is only one caller of __bad_area that passes in PKUERR and thus
> will generate a siginfo with si_pkey set.  Therefore simplify the
> logic and hoist reading of vma_pkey up into that caller, and just
> pass *pkey into __bad_area.
> 
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> ---
>  arch/x86/mm/fault.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index f82106578364..11a93f14a674 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -904,22 +904,16 @@ bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
>  
>  static void
>  __bad_area(struct pt_regs *regs, unsigned long error_code,
> -	   unsigned long address,  struct vm_area_struct *vma, int si_code)
> +	   unsigned long address, u32 *pkey, int si_code)
>  {
>  	struct mm_struct *mm = current->mm;
> -	u32 pkey;
> -
> -	if (vma)
> -		pkey = vma_pkey(vma);
> -
>  	/*
>  	 * Something tried to access memory that isn't in our memory map..
>  	 * Fix it, but check if it's kernel or user first..
>  	 */
>  	up_read(&mm->mmap_sem);
>  
> -	__bad_area_nosemaphore(regs, error_code, address,
> -			       (vma) ? &pkey : NULL, si_code);
> +	__bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
>  }
>  
>  static noinline void
> @@ -954,10 +948,12 @@ bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
>  	 * But, doing it this way allows compiler optimizations
>  	 * if pkeys are compiled out.
>  	 */
> -	if (bad_area_access_from_pkeys(error_code, vma))
> -		__bad_area(regs, error_code, address, vma, SEGV_PKUERR);
> +	if (bad_area_access_from_pkeys(error_code, vma)) {
> +		u32 pkey = vma_pkey(vma);
> +		__bad_area(regs, error_code, address, &pkey, SEGV_PKUERR);
> +	}
>  	else
> -		__bad_area(regs, error_code, address, vma, SEGV_ACCERR);
> +		__bad_area(regs, error_code, address, NULL, SEGV_ACCERR);

Please make that:

	} else {
		__bad_area(regs, error_code, address, NULL, SEGV_ACCERR);
	}
       
With that fixed:

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>