linux-kernel - Re: [PATCH 2/2 resend] mm: various cleanups in get_user

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Date:	Wed, 13 Feb 2008 12:13:04 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Eugene Teo <eugeneteo@...nel.sg>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, corbet@....net
Subject: Re: [PATCH 2/2 resend] mm: various cleanups in get_user_pages()

On Wednesday 13 February 2008 00:10, Eugene Teo wrote:
> Sorry for the repeated emails. Kindly ignore the previous resend. Please
> review this instead. Thanks. I have tested this.

If it is causing this much problems, can you split the cleanups into
their own patches.


> [PATCH 2/2] mm: various cleanups in get_user_pages()
>
> This patch contains various cleanups, including making sure vma is valid,
> and the return value of follow_hugetlb_page() is validated.
>
> Signed-off-by: Eugene Teo <eugeneteo@...nel.sg>
> ---
>  mm/memory.c |   24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 54f951b..c7e0610 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1003,7 +1003,9 @@ int get_user_pages(struct task_struct *tsk, struct
> mm_struct *mm, unsigned int foll_flags;
>
>  		vma = find_extend_vma(mm, start);
> -		if (!vma && in_gate_area(tsk, start)) {
> +		if (!vma)
> +			goto finish_or_fault;
> +		if (in_gate_area(tsk, start)) {
>  			unsigned long pg = start & PAGE_MASK;
>  			struct vm_area_struct *gate_vma = get_gate_vma(tsk);
>  			pgd_t *pgd;

Doesn't this break the logic?

If you don't have a vma, but you are in the gate area, then you
should use the gate vma. With your patch, gate area will fault.

> @@ -1011,7 +1013,7 @@ int get_user_pages(struct task_struct *tsk, struct
> mm_struct *mm, pmd_t *pmd;
>  			pte_t *pte;
>  			if (write) /* user gate pages are read-only */
> -				return i ? : -EFAULT;
> +				goto finish_or_fault;

I don't know if this is exactly a cleanup or not... I guess gcc
probably isn't smart enough to fold them all together, so it should
use a little less code in the unlikely branches. Does it?
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