pktgen: use dynamic allocation for debug print buffer

arndb · davem330 · commit a870a02cc963 · 2018-03-13T20:25:26.000-04:00
After the removal of the VLA, we get a harmless warning about a large stack frame: net/core/pktgen.c: In function 'pktgen_if_write': net/core/pktgen.c:1710:1: error: the frame size of 1076 bytes is larger than 1024 bytes [-Werror=frame-larger-than=] The function was previously shown to be safe despite hitting the 1024 bye warning level. To get rid of the annoyging warning, while keeping it readable, this changes it to use strndup_user(). Obviously this is not a fast path, so the kmalloc() overhead can be disregarded. Fixes: 3595139 ("pktgen: Remove VLA usage") Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
@@ -906,13 +906,14 @@ static ssize_t pktgen_if_write(struct file *file,
 	i += len;
 
 	if (debug) {
-		size_t copy = min_t(size_t, count, 1023);
-		char tb[1024];
-		if (copy_from_user(tb, user_buffer, copy))
-			return -EFAULT;
-		tb[copy] = 0;
-		pr_debug("%s,%lu  buffer -:%s:-\n",
-			 name, (unsigned long)count, tb);
+		size_t copy = min_t(size_t, count + 1, 1024);
+		char *tp = strndup_user(user_buffer, copy);
+
+		if (IS_ERR(tp))
+			return PTR_ERR(tp);
+
+		pr_debug("%s,%zu  buffer -:%s:-\n", name, count, tp);
+		kfree(buf);
 	}
 
 	if (!strcmp(name, "min_pkt_size")) {
