[v2] ARM/dma-mapping: use kvcalloc for fallback memory allocation need

[PATCH v2] ARM/dma-mapping: use kvcalloc for fallback memory allocation need

Posted by Deepak R Varma 2 years, 9 months ago

Current conditional determination of whether to use kzalloc or vzalloc
has known issues such as "indefinite retry" when less than PAGE_SIZE
memory is needed, but is unavailable. This LWN article [1] describes
these issues in greater detail. Use helper function kvcalloc() instead
which is more efficient in terms of performance and security.

 	[1] https://lwn.net/Articles/711653/

This patch proposal is based on following Coccinelle warning using the
kvmalloc.cocci semantic patch.
	arch/arm/mm/dma-mapping.c:858:28-29: WARNING opportunity for kvmalloc

The semantic patch suggests using kvzalloc() helper function, however,
this patch proposes to use kvcalloc instead. kvcalloc() helper function
uses 2-factor argument form which is better from a security perspective
as described in the following KSPP project commit.

	Commit 4e3fd7217105 ("wireguard: ratelimiter: use kvcalloc() instead of kvzalloc()")

Signed-off-by: Deepak R Varma <drv@mailo.com>
---

Changes in v2:
   1. Update patch subject to use kvcalloc
   2. Use kvcalloc instead of kvzalloc helper function. Revise the patch
      proposal and the patch description accordingly.


 arch/arm/mm/dma-mapping.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index c135f6e37a00..35092ecd30e1 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -851,14 +851,10 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
 {
 	struct page **pages;
 	int count = size >> PAGE_SHIFT;
-	int array_size = count * sizeof(struct page *);
 	int i = 0;
 	int order_idx = 0;

-	if (array_size <= PAGE_SIZE)
-		pages = kzalloc(array_size, GFP_KERNEL);
-	else
-		pages = vzalloc(array_size);
+	pages = kvcalloc(count, sizeof(struct page *), GFP_KERNEL);
 	if (!pages)
 		return NULL;

--
2.34.1

Re: [PATCH v2] ARM/dma-mapping: use kvcalloc for fallback memory allocation need

Posted by Deepak R Varma 2 years, 8 months ago

On Tue, Dec 20, 2022 at 07:46:32PM +0530, Deepak R Varma wrote:
> Current conditional determination of whether to use kzalloc or vzalloc
> has known issues such as "indefinite retry" when less than PAGE_SIZE
> memory is needed, but is unavailable. This LWN article [1] describes
> these issues in greater detail. Use helper function kvcalloc() instead
> which is more efficient in terms of performance and security.
>
>  	[1] https://lwn.net/Articles/711653/
>
> This patch proposal is based on following Coccinelle warning using the
> kvmalloc.cocci semantic patch.
> 	arch/arm/mm/dma-mapping.c:858:28-29: WARNING opportunity for kvmalloc
>
> The semantic patch suggests using kvzalloc() helper function, however,
> this patch proposes to use kvcalloc instead. kvcalloc() helper function
> uses 2-factor argument form which is better from a security perspective
> as described in the following KSPP project commit.
>
> 	Commit 4e3fd7217105 ("wireguard: ratelimiter: use kvcalloc() instead of kvzalloc()")
>
> Signed-off-by: Deepak R Varma <drv@mailo.com>

Hello,
May I please request a review and feedback on this patch proposal?

Thank you,
./drv

> ---
>
> Changes in v2:
>    1. Update patch subject to use kvcalloc
>    2. Use kvcalloc instead of kvzalloc helper function. Revise the patch
>       proposal and the patch description accordingly.
>
>
>  arch/arm/mm/dma-mapping.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index c135f6e37a00..35092ecd30e1 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -851,14 +851,10 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
>  {
>  	struct page **pages;
>  	int count = size >> PAGE_SHIFT;
> -	int array_size = count * sizeof(struct page *);
>  	int i = 0;
>  	int order_idx = 0;
>
> -	if (array_size <= PAGE_SIZE)
> -		pages = kzalloc(array_size, GFP_KERNEL);
> -	else
> -		pages = vzalloc(array_size);
> +	pages = kvcalloc(count, sizeof(struct page *), GFP_KERNEL);
>  	if (!pages)
>  		return NULL;
>
> --
> 2.34.1
>

Re: [PATCH v2] ARM/dma-mapping: use kvcalloc for fallback memory allocation need

Posted by Russell King (Oracle) 2 years, 8 months ago

On Wed, Dec 28, 2022 at 03:49:44PM +0530, Deepak R Varma wrote:
> On Tue, Dec 20, 2022 at 07:46:32PM +0530, Deepak R Varma wrote:
> > Current conditional determination of whether to use kzalloc or vzalloc
> > has known issues such as "indefinite retry" when less than PAGE_SIZE
> > memory is needed, but is unavailable. This LWN article [1] describes
> > these issues in greater detail. Use helper function kvcalloc() instead
> > which is more efficient in terms of performance and security.
> >
> >  	[1] https://lwn.net/Articles/711653/
> >
> > This patch proposal is based on following Coccinelle warning using the
> > kvmalloc.cocci semantic patch.
> > 	arch/arm/mm/dma-mapping.c:858:28-29: WARNING opportunity for kvmalloc
> >
> > The semantic patch suggests using kvzalloc() helper function, however,
> > this patch proposes to use kvcalloc instead. kvcalloc() helper function
> > uses 2-factor argument form which is better from a security perspective
> > as described in the following KSPP project commit.
> >
> > 	Commit 4e3fd7217105 ("wireguard: ratelimiter: use kvcalloc() instead of kvzalloc()")
> >
> > Signed-off-by: Deepak R Varma <drv@mailo.com>
> 
> Hello,
> May I please request a review and feedback on this patch proposal?

The DMA API on ARM has been maintained by others recently, so it's no
longer up to me. Please include Christoph Hellwig <hch@lst.de> when
sending changes for this. Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

Re: [PATCH v2] ARM/dma-mapping: use kvcalloc for fallback memory allocation need

Posted by Deepak R Varma 2 years, 8 months ago

On Tue, Jan 03, 2023 at 10:19:20AM +0000, Russell King (Oracle) wrote:
> On Wed, Dec 28, 2022 at 03:49:44PM +0530, Deepak R Varma wrote:
> > On Tue, Dec 20, 2022 at 07:46:32PM +0530, Deepak R Varma wrote:
> > > Current conditional determination of whether to use kzalloc or vzalloc
> > > has known issues such as "indefinite retry" when less than PAGE_SIZE
> > > memory is needed, but is unavailable. This LWN article [1] describes
> > > these issues in greater detail. Use helper function kvcalloc() instead
> > > which is more efficient in terms of performance and security.
> > >
> > >  	[1] https://lwn.net/Articles/711653/
> > >
> > > This patch proposal is based on following Coccinelle warning using the
> > > kvmalloc.cocci semantic patch.
> > > 	arch/arm/mm/dma-mapping.c:858:28-29: WARNING opportunity for kvmalloc
> > >
> > > The semantic patch suggests using kvzalloc() helper function, however,
> > > this patch proposes to use kvcalloc instead. kvcalloc() helper function
> > > uses 2-factor argument form which is better from a security perspective
> > > as described in the following KSPP project commit.
> > >
> > > 	Commit 4e3fd7217105 ("wireguard: ratelimiter: use kvcalloc() instead of kvzalloc()")
> > >
> > > Signed-off-by: Deepak R Varma <drv@mailo.com>
> >
> > Hello,
> > May I please request a review and feedback on this patch proposal?
>
> The DMA API on ARM has been maintained by others recently, so it's no
> longer up to me. Please include Christoph Hellwig <hch@lst.de> when
> sending changes for this. Thanks.

Sure. Actually the get_maintainer.pl scripts still returns yourself as the
maintainer for this driver. Hence the email to you.
I will send a v3 and include the change you asked for. I will keep you in cc if
you don't mind.

Also, let me know if I can help with getting the maintainer list updated for
this core subsystem.

Thank you,
./drv

>
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!