cw1200: Don't leak memory if krealloc failes

The call to krealloc() in wsm_buf_reserve() directly assigns the newly
returned memory to buf->begin. This is all fine except when krealloc()
failes we loose the ability to free the old memory pointed to by
buf->begin. If we just create a temporary variable to assign memory to
and assign the memory to it we can mitigate the memory leak.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/st/cw1200/wsm.c

@@ -1807,16 +1807,18 @@ static int wsm_buf_reserve(struct wsm_buf *buf, size_t extra_size)
 {
 	size_t pos = buf->data - buf->begin;
 	size_t size = pos + extra_size;
+	u8 *tmp;
 
 	size = round_up(size, FWLOAD_BLOCK_SIZE);
 
-	buf->begin = krealloc(buf->begin, size, GFP_KERNEL | GFP_DMA);
-	if (buf->begin) {
+	tmp = krealloc(buf->begin, size, GFP_KERNEL | GFP_DMA);
+	if (!tmp) {
+		wsm_buf_deinit(buf);
+		return -ENOMEM;
+	}
+
+	buf->begin = tmp;
 	buf->data = &buf->begin[pos];
 	buf->end = &buf->begin[size];
 	return 0;
-	} else {
-		buf->end = buf->data = buf->begin;
-		return -ENOMEM;
-	}
 }