Re: [PATCH] amd_iommu: Fix leak in free_pagetable()

[Alex Williamson]

On Thu, 2013-06-20 at 20:28 +0200, Joerg Roedel wrote:
> On Mon, Jun 17, 2013 at 07:52:14PM -0600, Alex Williamson wrote:
> >  static void free_pagetable(struct protection_domain *domain)
> >  {
> > -	int i, j;
> > -	u64 *p1, *p2, *p3;
> > +	int i, j, k, l, m, depth = domain->mode;
> > +	u64 *p1, *p2, *p3, *p4, *p5, *p6;
> >  
> >  	p1 = domain->pt_root;
> >  
> >  	if (!p1)
> >  		return;
> >  
> > -	for (i = 0; i < 512; ++i) {
> > +	for (i = 0; depth > 1 && i < 512; ++i) {
> >  		if (!IOMMU_PTE_PRESENT(p1[i]))
> >  			continue;
> >  
> >  		p2 = IOMMU_PTE_PAGE(p1[i]);
> > -		for (j = 0; j < 512; ++j) {
> > +		for (j = 0; depth > 2 && j < 512; ++j) {
> >  			if (!IOMMU_PTE_PRESENT(p2[j]))
> >  				continue;
> > +
> >  			p3 = IOMMU_PTE_PAGE(p2[j]);
> > +			for (k = 0; depth > 3 && k < 512; ++k) {
> > +				if (!IOMMU_PTE_PRESENT(p3[k]))
> > +					continue;
> > +
> > +				p4 = IOMMU_PTE_PAGE(p3[k]);
> > +				for (l = 0; depth > 4 && l < 512; ++l) {
> > +					if (!IOMMU_PTE_PRESENT(p4[l]))
> > +						continue;
> > +
> > +					p5 = IOMMU_PTE_PAGE(p4[l]);
> > +					for (m = 0; depth > 5 && m < 512; ++m) {
> > +						if (!IOMMU_PTE_PRESENT(p5[m]))
> > +							continue;
> > +						p6 = IOMMU_PTE_PAGE(p5[m]);
> > +						free_page((unsigned long)p6);
> > +					}
> > +
> > +					free_page((unsigned long)p5);
> > +				}
> > +
> > +				free_page((unsigned long)p4);
> > +			}
> > +
> >  			free_page((unsigned long)p3);
> >  		}
> 
> Hmm, actually a recursive version would make more sense here. But since
> recursion is a bad idea in the kernel, how about this approach instead:

It's a fixed maximum depth of recursion though, is it really that taboo?

> From d500d538ad1370679d05667663dcaf8603d529db Mon Sep 17 00:00:00 2001
> From: Joerg Roedel <joro@xxxxxxxxxx>
> Date: Thu, 20 Jun 2013 20:22:58 +0200
> Subject: [PATCH] iommu/amd: Fix memory leak in free_pagetable
> 
> The IOMMU pagetables can have up to 3 levels, but the code

s/3/6/

> in free_pagetable() only releases the first 3 levels. Fix
> this leak by releasing all levels.
> 
> Reported-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Signed-off-by: Joerg Roedel <joro@xxxxxxxxxx>
> ---
>  drivers/iommu/amd_iommu.c |   73 ++++++++++++++++++++++++++++++---------------
>  1 file changed, 49 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 21d02b0..5cde682 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -1893,34 +1893,59 @@ static void domain_id_free(int id)
>  	write_unlock_irqrestore(&amd_iommu_devtable_lock, flags);
>  }
>  
> +#define DEFINE_FREE_PT_FN(LVL, FN)				\
> +static void free_pt_##LVL (unsigned long __pt)			\
> +{								\
> +	unsigned long p;					\
> +	u64 *pt;						\
> +	int i;							\
> +								\
> +	pt = (u64 *)__pt;					\
> +								\
> +	for (i = 0; i < 512; ++i) {				\
> +		if (!IOMMU_PTE_PRESENT(pt[i]))			\
> +			continue;				\
> +								\
> +		p = (unsigned long)IOMMU_PTE_PAGE(pt[i]);	\
> +		FN(p);						\
> +	}							\
> +	free_page((unsigned long)pt);				\
> +}
> +
> +DEFINE_FREE_PT_FN(l2, free_page)
> +DEFINE_FREE_PT_FN(l3, free_pt_l2)
> +DEFINE_FREE_PT_FN(l4, free_pt_l3)
> +DEFINE_FREE_PT_FN(l5, free_pt_l4)
> +DEFINE_FREE_PT_FN(l6, free_pt_l5)
> +
>  static void free_pagetable(struct protection_domain *domain)
>  {
> -	int i, j;
> -	u64 *p1, *p2, *p3;
> -
> -	p1 = domain->pt_root;
> -
> -	if (!p1)
> -		return;
> -
> -	for (i = 0; i < 512; ++i) {
> -		if (!IOMMU_PTE_PRESENT(p1[i]))
> -			continue;
> +	unsigned long root = (unsigned long)domain->pt_root;
>  
> -		p2 = IOMMU_PTE_PAGE(p1[i]);
> -		for (j = 0; j < 512; ++j) {
> -			if (!IOMMU_PTE_PRESENT(p2[j]))
> -				continue;
> -			p3 = IOMMU_PTE_PAGE(p2[j]);
> -			free_page((unsigned long)p3);
> -		}
> -
> -		free_page((unsigned long)p2);
> +	switch (domain->mode) {
> +	case PAGE_MODE_NONE:
> +		break;
> +	case PAGE_MODE_1_LEVEL:
> +		free_page(root);
> +		break;
> +	case PAGE_MODE_2_LEVEL:
> +		free_pt_l2(root);
> +		break;
> +	case PAGE_MODE_3_LEVEL:
> +		free_pt_l3(root);
> +		break;
> +	case PAGE_MODE_4_LEVEL:
> +		free_pt_l4(root);
> +		break;
> +	case PAGE_MODE_5_LEVEL:
> +		free_pt_l5(root);
> +		break;
> +	case PAGE_MODE_6_LEVEL:
> +		free_pt_l6(root);
> +		break;
> +	default:
> +		BUG();
>  	}
> -
> -	free_page((unsigned long)p1);
> -
> -	domain->pt_root = NULL;
>  }
>  
>  static void free_gcr3_tbl_level1(u64 *tbl)

Seems like it should do the right thing

Reviewed-by: Alex Williamson <alex.williamson@xxxxxxxxxx>

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