staging: ion: Fix possible null pointer dereference

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.

Acked-by: Colin Cross <ccross@android.com>
Cc: Android Kernel Team <kernel-team@android.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
index 05e9dc93980fdea852012739d9867eecfe0d2bb1..5bccf9e2c93c0b7291345ebf9b73cc6b73862b6e 100644 (file)
--- 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;
 }