[PATCH v2 0/2] dma-contiguous: two bug fixes for dma_{alloc,free}_contiguous()

[PATCH v2 0/2] dma-contiguous: two bug fixes for dma_{alloc,free}_contiguous()

[Nicolin Chen]

There are two obvious bugs in these two functions. So having
two patches to fix them.

Changlog
v1->v2:
 * PATCH-1: Confine cma_align inside the if-condition.
 * PATCH-1: Updated commit message to be precise for the corner case.
 * PATCH-2: Added Reviewed-by from Christoph.

Nicolin Chen (2):
  dma-contiguous: do not overwrite align in dma_alloc_contiguous()
  dma-contiguous: page-align the size in dma_free_contiguous()

 kernel/dma/contiguous.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

-- 
2.17.1

[PATCH v2 1/2] dma-contiguous: do not overwrite align in dma_alloc_contiguous()

[Nicolin Chen]

The dma_alloc_contiguous() limits align at CONFIG_CMA_ALIGNMENT for
cma_alloc() however it does not restore it for the fallback routine.
This will result in a size mismatch between the allocation and free
when running into the fallback routines after cma_alloc() fails, if
the align is larger than CONFIG_CMA_ALIGNMENT.

This patch adds a cma_align to take care of cma_alloc() and prevent
the align from being overwritten.

Fixes: fdaeec198ada ("dma-contiguous: add dma_{alloc,free}_contiguous() helpers")
Reported-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
---
 kernel/dma/contiguous.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index bfc0c17f2a3d..ea8259f53eda 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -243,8 +243,9 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
 
 	/* CMA can be used only in the context which permits sleeping */
 	if (cma && gfpflags_allow_blocking(gfp)) {
-		align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT);
-		page = cma_alloc(cma, count, align, gfp & __GFP_NOWARN);
+		size_t cma_align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT);
+
+		page = cma_alloc(cma, count, cma_align, gfp & __GFP_NOWARN);
 	}
 
 	/* Fallback allocation of normal pages */
-- 
2.17.1

[PATCH v2 2/2] dma-contiguous: page-align the size in dma_free_contiguous()

[Nicolin Chen]

According to the original dma_direct_alloc_pages() code:
{
	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;

	if (!dma_release_from_contiguous(dev, page, count))
		__free_pages(page, get_order(size));
}

The count parameter for dma_release_from_contiguous() was page
aligned before the right-shifting operation, while the new API
dma_free_contiguous() forgets to have PAGE_ALIGN() at the size.

So this patch simply adds it to prevent any corner case.

Fixes: fdaeec198ada ("dma-contiguous: add dma_{alloc,free}_contiguous() helpers")
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 kernel/dma/contiguous.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index ea8259f53eda..2bd410f934b3 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -267,7 +267,8 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
  */
 void dma_free_contiguous(struct device *dev, struct page *page, size_t size)
 {
-	if (!cma_release(dev_get_cma_area(dev), page, size >> PAGE_SHIFT))
+	if (!cma_release(dev_get_cma_area(dev), page,
+			 PAGE_ALIGN(size) >> PAGE_SHIFT))
 		__free_pages(page, get_order(size));
 }
 
-- 
2.17.1

Re: [PATCH v2 0/2] dma-contiguous: two bug fixes for dma_{alloc,free}_contiguous()

[Christoph Hellwig]

Thanks,

applied to the dma-mapping for-linus tree.