[PATCH 4.15 102/105] staging: android: ion: Zero CMA allocated memory

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Liam Mark <lmark@xxxxxxxxxxxxxx>

commit 6d79bd5bb6c79a9dba4842040c9adf39e7806330 upstream.

Since commit 204f672255c2 ("staging: android: ion: Use CMA APIs directly")
the CMA API is now used directly and therefore the allocated memory is no
longer automatically zeroed.

Explicitly zero CMA allocated memory to ensure that no data is exposed to
userspace.

Fixes: 204f672255c2 ("staging: android: ion: Use CMA APIs directly")
Signed-off-by: Liam Mark <lmark@xxxxxxxxxxxxxx>
Acked-by: Laura Abbott <labbott@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/staging/android/ion/ion_cma_heap.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

--- a/drivers/staging/android/ion/ion_cma_heap.c
+++ b/drivers/staging/android/ion/ion_cma_heap.c
@@ -21,6 +21,7 @@
 #include <linux/err.h>
 #include <linux/cma.h>
 #include <linux/scatterlist.h>
+#include <linux/highmem.h>
 
 #include "ion.h"
 
@@ -51,6 +52,22 @@ static int ion_cma_allocate(struct ion_h
 	if (!pages)
 		return -ENOMEM;
 
+	if (PageHighMem(pages)) {
+		unsigned long nr_clear_pages = nr_pages;
+		struct page *page = pages;
+
+		while (nr_clear_pages > 0) {
+			void *vaddr = kmap_atomic(page);
+
+			memset(vaddr, 0, PAGE_SIZE);
+			kunmap_atomic(vaddr);
+			page++;
+			nr_clear_pages--;
+		}
+	} else {
+		memset(page_address(pages), 0, size);
+	}
+
 	table = kmalloc(sizeof(*table), GFP_KERNEL);
 	if (!table)
 		goto err;