[PATCH 17/32] net/flow_offload: Use mem_to_flex_dup() with struct flow_action_cookie

[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: Baowen Zheng <baowen.zheng at corigine.com>
Cc: Eli Cohen <elic at nvidia.com>
Cc: Louis Peens <louis.peens at corigine.com>
Cc: Simon Horman <simon.horman at corigine.com>
Cc: netdev at vger.kernel.org
Signed-off-by: Kees Cook <keescook at chromium.org>
---
 include/net/flow_offload.h | 4 ++--
 net/core/flow_offload.c    | 7 ++-----
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
index 021778a7e1af..ca5db457a0bc 100644
--- a/include/net/flow_offload.h
+++ b/include/net/flow_offload.h
@@ -190,8 +190,8 @@ enum flow_action_hw_stats {
 typedef void (*action_destr)(void *priv);
 
 struct flow_action_cookie {
-	u32 cookie_len;
-	u8 cookie[];
+	DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(u32, cookie_len);
+	DECLARE_FLEX_ARRAY_ELEMENTS(u8, cookie);
 };
 
 struct flow_action_cookie *flow_action_cookie_create(void *data,
diff --git a/net/core/flow_offload.c b/net/core/flow_offload.c
index 73f68d4625f3..e23c8d05b828 100644
--- a/net/core/flow_offload.c
+++ b/net/core/flow_offload.c
@@ -199,13 +199,10 @@ struct flow_action_cookie *flow_action_cookie_create(void *data,
 						     unsigned int len,
 						     gfp_t gfp)
 {
-	struct flow_action_cookie *cookie;
+	struct flow_action_cookie *cookie = NULL;
 
-	cookie = kmalloc(sizeof(*cookie) + len, gfp);
-	if (!cookie)
+	if (mem_to_flex_dup(&cookie, data, len, gfp))
 		return NULL;
-	cookie->cookie_len = len;
-	memcpy(cookie->cookie, data, len);
 	return cookie;
 }
 EXPORT_SYMBOL(flow_action_cookie_create);
-- 
2.32.0