[PATCH] arm64/dma-mapping: Fix null-pointer check

[Olav Haugan]

The current null-pointer check in __dma_alloc_coherent and
__dma_free_coherent is pretty much useless since we are dereferencing
the pointer before checking for null.
Check for null-pointer before the actual dereferencing of the pointer.

Signed-off-by: Olav Haugan <ohau...@codeaurora.org>
---
 arch/arm64/mm/dma-mapping.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 3216e098c058..a4b65773711d 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -95,11 +95,6 @@ static void *__dma_alloc_coherent(struct device *dev, size_t 
size,
                                  dma_addr_t *dma_handle, gfp_t flags,
                                  unsigned long attrs)
 {
-       if (dev == NULL) {
-               WARN_ONCE(1, "Use an actual device structure for DMA 
allocation\n");
-               return NULL;
-       }
-
        if (IS_ENABLED(CONFIG_ZONE_DMA) &&
            dev->coherent_dma_mask <= DMA_BIT_MASK(32))
                flags |= GFP_DMA;
@@ -128,10 +123,6 @@ static void __dma_free_coherent(struct device *dev, size_t 
size,
        bool freed;
        phys_addr_t paddr = dma_to_phys(dev, dma_handle);
 
-       if (dev == NULL) {
-               WARN_ONCE(1, "Use an actual device structure for DMA 
allocation\n");
-               return;
-       }
 
        freed = dma_release_from_contiguous(dev,
                                        phys_to_page(paddr),
@@ -149,6 +140,11 @@ static void *__dma_alloc(struct device *dev, size_t size,
        bool coherent = is_device_dma_coherent(dev);
        pgprot_t prot = __get_dma_pgprot(attrs, PAGE_KERNEL, false);
 
+       if (!dev) {
+               WARN_ONCE(1, "Use an actual device structure for DMA 
allocation\n");
+               return NULL;
+       }
+
        size = PAGE_ALIGN(size);
 
        if (!coherent && !gfpflags_allow_blocking(flags)) {
@@ -192,8 +188,13 @@ static void __dma_free(struct device *dev, size_t size,
                       void *vaddr, dma_addr_t dma_handle,
                       unsigned long attrs)
 {
-       void *swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle));
+       void *swiotlb_addr;
 
+       if (!dev) {
+               WARN_ONCE(1, "Use an actual device structure for DMA free\n");
+               return;
+       }
+       swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle));
        size = PAGE_ALIGN(size);
 
        if (!is_device_dma_coherent(dev)) {
-- 
2.13.0