ALSA: hda: Fix krealloc() with __GFP_ZERO usage

commit 33baefe5 upstream.

krealloc() doesn't work always properly with __GFP_ZERO flag as
expected.  For clearing the reallocated area, we need to clear
explicitly instead.
Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

sound/pci/hda/hda_codec.c

@@ -5793,13 +5793,15 @@ void *snd_array_new(struct snd_array *array)
 		return NULL;
 	if (array->used >= array->alloced) {
 		int num = array->alloced + array->alloc_align;
+		int oldsize = array->alloced * array->elem_size;
 		int size = (num + 1) * array->elem_size;
 		void *nlist;
 		if (snd_BUG_ON(num >= 4096))
 			return NULL;
-		nlist = krealloc(array->list, size, GFP_KERNEL | __GFP_ZERO);
+		nlist = krealloc(array->list, size, GFP_KERNEL);
 		if (!nlist)
 			return NULL;
+		memset(nlist + oldsize, 0, size - oldsize);
 		array->list = nlist;
 		array->alloced = num;
 	}