[PATCH 15/32] 802/garp: Use mem_to_flex_dup() with struct garp_attr

[Kees Cook <keescook@chromium.org>]

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

diff --git a/include/net/garp.h b/include/net/garp.h
index 4d9a0c6a2e5f..ec087ae534e7 100644
--- a/include/net/garp.h
+++ b/include/net/garp.h
@@ -80,8 +80,8 @@ struct garp_attr {
 	struct rb_node			node;
 	enum garp_applicant_state	state;
 	u8				type;
-	u8				dlen;
-	unsigned char			data[];
+	DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(u8, dlen);
+	DECLARE_FLEX_ARRAY_ELEMENTS(unsigned char, data);
 };
 
 enum garp_applications {
diff --git a/net/802/garp.c b/net/802/garp.c
index f6012f8e59f0..72743ed00a54 100644
--- a/net/802/garp.c
+++ b/net/802/garp.c
@@ -168,7 +168,7 @@ static struct garp_attr *garp_attr_create(struct garp_applicant *app,
 					  const void *data, u8 len, u8 type)
 {
 	struct rb_node *parent = NULL, **p = &app->gid.rb_node;
-	struct garp_attr *attr;
+	struct garp_attr *attr = NULL;
 	int d;
 
 	while (*p) {
@@ -184,13 +184,10 @@ static struct garp_attr *garp_attr_create(struct garp_applicant *app,
 			return attr;
 		}
 	}
-	attr = kmalloc(sizeof(*attr) + len, GFP_ATOMIC);
-	if (!attr)
-		return attr;
+	if (mem_to_flex_dup(&attr, data, len, GFP_ATOMIC))
+		return NULL;
 	attr->state = GARP_APPLICANT_VO;
 	attr->type  = type;
-	attr->dlen  = len;
-	memcpy(attr->data, data, len);
 
 	rb_link_node(&attr->node, parent, p);
 	rb_insert_color(&attr->node, &app->gid);
-- 
2.32.0