[PATCH 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 in the fallback routines, 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@xxxxxxxxxxxxx>
Signed-off-by: Nicolin Chen <nicoleotsuka@xxxxxxxxx>
---
 kernel/dma/contiguous.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index bfc0c17f2a3d..fa8cd0f0512e 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -233,6 +233,7 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
 	int node = dev ? dev_to_node(dev) : NUMA_NO_NODE;
 	size_t count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	size_t align = get_order(PAGE_ALIGN(size));
+	size_t cma_align = CONFIG_CMA_ALIGNMENT;
 	struct page *page = NULL;
 	struct cma *cma = NULL;
 
@@ -241,11 +242,11 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
 	else if (count > 1)
 		cma = dma_contiguous_default_area;
 
+	cma_align = min_t(size_t, align, cma_align);
+
 	/* 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);
-	}
+	if (cma && gfpflags_allow_blocking(gfp))
+		page = cma_alloc(cma, count, cma_align, gfp & __GFP_NOWARN);
 
 	/* Fallback allocation of normal pages */
 	if (!page)
-- 
2.17.1