From f64cfa931a450ffb08cbbdeb6652b424f6bb8187 Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Thu, 30 Jan 2020 14:12:35 -0800
Subject: [PATCH] Avoid use of alloca and statement expressions

---
 include/netlink-private/utils.h | 21 ---------------------
 lib/genl/mngt.c                 | 13 +++++++++----
 2 files changed, 9 insertions(+), 25 deletions(-)

diff --git a/include/netlink-private/utils.h b/include/netlink-private/utils.h
index 1456797..e26399f 100644
--- a/include/netlink-private/utils.h
+++ b/include/netlink-private/utils.h
@@ -93,27 +93,6 @@ extern const char *nl_strerror_l(int err);
 
 /*****************************************************************************/
 
-#define _nl_malloc_maybe_a(alloca_maxlen, bytes, to_free) \
-	({ \
-		const size_t _bytes = (bytes); \
-		__typeof__ (to_free) _to_free = (to_free); \
-		__typeof__ (*_to_free) _ptr; \
-		\
-		_NL_STATIC_ASSERT ((alloca_maxlen) <= 500); \
-		_nl_assert (_to_free && !*_to_free); \
-		\
-		if (_bytes <= (alloca_maxlen)) { \
-			_ptr = alloca (_bytes); \
-		} else { \
-			_ptr = malloc (_bytes); \
-			*_to_free = _ptr; \
-		}; \
-		\
-		_ptr; \
-	})
-
-/*****************************************************************************/
-
 static inline char *
 _nl_strncpy_trunc(char *dst, const char *src, size_t len)
 {
diff --git a/lib/genl/mngt.c b/lib/genl/mngt.c
index ff50e1d..8f92122 100644
--- a/lib/genl/mngt.c
+++ b/lib/genl/mngt.c
@@ -54,7 +54,7 @@ static int cmd_msg_parser(struct sockaddr_nl *who, struct nlmsghdr *nlh,
 	int err;
 	struct genlmsghdr *ghdr;
 	struct genl_cmd *cmd;
-	struct nlattr **tb;
+	struct nlattr **tb, *tb_local[32];
 
 	ghdr = genlmsg_hdr(nlh);
 
@@ -64,9 +64,14 @@ static int cmd_msg_parser(struct sockaddr_nl *who, struct nlmsghdr *nlh,
 	if (cmd->c_msg_parser == NULL)
 		return -NLE_OPNOTSUPP;
 
-	tb = _nl_malloc_maybe_a (300, (((size_t) cmd->c_maxattr) + 1u) * sizeof (struct nlattr *), &tb_free);
-	if (!tb)
-		return -NLE_NOMEM;
+	if (cmd->c_maxattr > ARRAY_SIZE(tb_local) - 1) {
+		tb = malloc(((size_t) cmd->c_maxattr + 1u) * sizeof (struct nlattr *));
+		if (!tb)
+			return -NLE_NOMEM;
+		tb_free = tb;
+	} else {
+		tb = tb_local;
+	}
 
 	err = nlmsg_parse(nlh,
 	                  GENL_HDRSIZE(ops->o_hdrsize),
-- 
2.25.0