[PATCH 2/3] staging: ion: Fix possible null pointer dereference

[John Stultz <john.stultz@linaro.org>]

The kbuild test robot reported:

drivers/staging/android/ion/ion_system_heap.c:122 alloc_largest_available() error: potential null dereference 'info'.  (kmalloc returns null)

Where the pointer returned from kmalloc goes unchecked for failure.

This patch checks the return for NULL, and reworks the logic, as
suggested by Colin, so we allocate the page_info structure first.

Cc: Colin Cross <ccross@android.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Android Kernel Team <kernel-team@android.com>
Cc: kbuild test robot <fengguang.wu@intel.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 drivers/staging/android/ion/ion_system_heap.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
index 144b2272..7f07291 100644
--- a/drivers/staging/android/ion/ion_system_heap.c
+++ b/drivers/staging/android/ion/ion_system_heap.c
@@ -108,6 +108,10 @@ static struct page_info *alloc_largest_available(struct ion_system_heap *heap,
 	struct page_info *info;
 	int i;
 
+	info = kmalloc(sizeof(struct page_info), GFP_KERNEL);
+	if (!info)
+		return NULL;
+
 	for (i = 0; i < num_orders; i++) {
 		if (size < order_to_size(orders[i]))
 			continue;
@@ -118,11 +122,12 @@ static struct page_info *alloc_largest_available(struct ion_system_heap *heap,
 		if (!page)
 			continue;
 
-		info = kmalloc(sizeof(struct page_info), GFP_KERNEL);
 		info->page = page;
 		info->order = orders[i];
 		return info;
 	}
+	kfree(info);
+
 	return NULL;
 }
 
-- 
1.8.3.2