DMA, CMA: fix possible memory leak

We should free memory for bitmap when we find zone mismatch, otherwise
this memory will leak.

Additionally, I copy code comment from PPC KVM's CMA code to inform why
we need to check zone mis-match.

Signed-off-by: Joonsoo Kim <[e-mail]>
Acked-by: Zhang Yanfei <[e-mail]>
Reviewed-by: Michal Nazarewicz <[e-mail]>
Reviewed-by: Aneesh Kumar K.V <[e-mail]>
Acked-by: Minchan Kim <[e-mail]>
Cc: "Aneesh Kumar K.V" <[e-mail]>
Cc: Marek Szyprowski <[e-mail]>
Cc: Michal Nazarewicz <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>
Cc: Gleb Natapov <[e-mail]>
Cc: Alexander Graf <[e-mail]>
Cc: Benjamin Herrenschmidt <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/base/dma-contiguous.c

···
 		base_pfn = pfn;
 		for (j = pageblock_nr_pages; j; --j, pfn++) {
 			WARN_ON_ONCE(!pfn_valid(pfn));
+			/*
+			 * alloc_contig_range requires the pfn range
+			 * specified to be in the same zone. Make this
+			 * simple by forcing the entire CMA resv range
+			 * to be in the same zone.
+			 */
 			if (page_zone(pfn_to_page(pfn)) != zone)
-				return -EINVAL;
+				goto err;
 		}
 		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
 	} while (--i);
 
 	mutex_init(&cma->lock);
 	return 0;
+
+err:
+	kfree(cma->bitmap);
+	return -EINVAL;
 }
 
 static struct cma cma_areas[MAX_CMA_AREAS];