mm: cma: fix incorrect type conversion for size during dma allocation

This was found during userspace fuzzing test when a large size dma cma
allocation is made by driver(like ion) through userspace.

show_stack+0x10/0x1c
dump_stack+0x74/0xc8
kasan_report_error+0x2b0/0x408
kasan_report+0x34/0x40
__asan_storeN+0x15c/0x168
memset+0x20/0x44
__dma_alloc_coherent+0x114/0x18c

Signed-off-by: Rohit Vaswani <[e-mail]>
Acked-by: Greg Kroah-Hartman <[e-mail]>
Cc: Marek Szyprowski <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/base/dma-contiguous.c

···
  * global one. Requires architecture specific dev_get_cma_area() helper
  * function.
  */
-struct page *dma_alloc_from_contiguous(struct device *dev, int count,
+struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
 				       unsigned int align)
 {
 	if (align > CONFIG_CMA_ALIGNMENT)

include/linux/cma.h

···
 extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
 					unsigned int order_per_bit,
 					struct cma **res_cma);
-extern struct page *cma_alloc(struct cma *cma, unsigned int count, unsigned int align);
+extern struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align);
 extern bool cma_release(struct cma *cma, const struct page *pages, unsigned int count);
 #endif

include/linux/dma-contiguous.h

···
 	return ret;
 }
 
-struct page *dma_alloc_from_contiguous(struct device *dev, int count,
+struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
 				       unsigned int order);
 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
 				 int count);
···
 }
 
 static inline
-struct page *dma_alloc_from_contiguous(struct device *dev, int count,
+struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
 				       unsigned int order)
 {
 	return NULL;

mm/cma.c

···
  * This function allocates part of contiguous memory on specific
  * contiguous memory area.
  */
-struct page *cma_alloc(struct cma *cma, unsigned int count, unsigned int align)
+struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align)
 {
 	unsigned long mask, offset, pfn, start = 0;
 	unsigned long bitmap_maxno, bitmap_no, bitmap_count;
···
 	if (!cma || !cma->count)
 		return NULL;
 
-	pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
+	pr_debug("%s(cma %p, count %zu, align %d)\n", __func__, (void *)cma,
 		 count, align);
 
 	if (!count)