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

[Kees Cook <keescook@xxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: Hulk Robot <hulkci@xxxxxxxxxx>
Cc: Yang Yingliang <yangyingliang@xxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 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