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 <[email protected]>
---
Changes in v3:
1. Use updated maintainer list to send the patch.
Suggested by "Russell King (Oracle)" <[email protected]>
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
On Tue, Jan 03, 2023 at 04:26:38PM +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 <[email protected]>
> ---
> Changes in v3:
> 1. Use updated maintainer list to send the patch.
> Suggested by "Russell King (Oracle)" <[email protected]>
Hello,
May I request a review and feedback comment on this patch proposal please?
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
>