exynos-mem: Fix major security hole

This fixes the exynos-mem device security hole. The driver allowed any user
to access all of the device's lowmem through the provided mmap functionality.

We create a small little framework collecting the actual CMA memory blocks
that exist on the device; they are the root cause of the existence of this device
driver. We white-list only the CMA memory spaces as parameters to the mmap
function and deny access to any other memory space requests.

We furthermore just allow access to the "s3c-fimc" memory block as this is
seemingly the only space which upon access denial actually breaks functionality.

Change-Id: I286be4a2546621c66d214c79f480822ecd8138db

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/exynos_mem.h b/include/linux/exynos_mem.h
index 9c7bed9..3ed0bd6 100644
--- a/include/linux/exynos_mem.h
+++ b/include/linux/exynos_mem.h
@@ -22,4 +22,13 @@ struct exynos_mem_flush_range {
 	size_t		length;
 };
 
+#define CMA_REGION_COUNT (12)
+struct simple_cma_descriptor {
+	const char 	*name;
+	int		start;
+	int		size;
+};
+
+extern void cma_region_descriptor_add(const char *name, int start, int size);
+
 #endif /* __INCLUDE_EXYNOS_MEM_H */