[PATCH 16/32] 802/mrp: Use mem_to_flex_dup() with struct mrp_attr

[Kees Cook]

As part of the work to perform bounds checking on all memcpy() uses,
replace the open-coded a deserialization of bytes out of memory into a
trailing flexible array by using a flex_array.h helper to perform the
allocation, bounds checking, and copying.

Cc: "David S. Miller" <davem at davemloft.net>
Cc: Eric Dumazet <edumazet at google.com>
Cc: Jakub Kicinski <kuba at kernel.org>
Cc: Paolo Abeni <pabeni at redhat.com>
Cc: Yang Yingliang <yangyingliang at huawei.com>
Cc: netdev at vger.kernel.org
Signed-off-by: Kees Cook <keescook at chromium.org>
---
 include/net/mrp.h | 4 ++--
 net/802/mrp.c     | 9 +++------
 2 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/include/net/mrp.h b/include/net/mrp.h
index 1c308c034e1a..211670bb46f2 100644
--- a/include/net/mrp.h
+++ b/include/net/mrp.h
@@ -91,8 +91,8 @@ struct mrp_attr {
 	struct rb_node			node;
 	enum mrp_applicant_state	state;
 	u8				type;
-	u8				len;
-	unsigned char			value[];
+	DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(u8, len);
+	DECLARE_FLEX_ARRAY_ELEMENTS(unsigned char, value);
 };
 
 enum mrp_applications {
diff --git a/net/802/mrp.c b/net/802/mrp.c
index 35e04cc5390c..8b9b2e685a42 100644
--- a/net/802/mrp.c
+++ b/net/802/mrp.c
@@ -257,7 +257,7 @@ static struct mrp_attr *mrp_attr_create(struct mrp_applicant *app,
 					const void *value, u8 len, u8 type)
 {
 	struct rb_node *parent = NULL, **p = &app->mad.rb_node;
-	struct mrp_attr *attr;
+	struct mrp_attr *attr = NULL;
 	int d;
 
 	while (*p) {
@@ -273,13 +273,10 @@ static struct mrp_attr *mrp_attr_create(struct mrp_applicant *app,
 			return attr;
 		}
 	}
-	attr = kmalloc(sizeof(*attr) + len, GFP_ATOMIC);
-	if (!attr)
-		return attr;
+	if (mem_to_flex_dup(&attr, value, len, GFP_ATOMIC))
+		return NULL;
 	attr->state = MRP_APPLICANT_VO;
 	attr->type  = type;
-	attr->len   = len;
-	memcpy(attr->value, value, len);
 
 	rb_link_node(&attr->node, parent, p);
 	rb_insert_color(&attr->node, &app->mad);
-- 
2.32.0