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

[Nicolin Chen <nicoleotsuka@gmail.com>]

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