caif: Define usercopy region in caif proto slab cache

The CAIF channel connection request parameters need to be copied to/from
userspace. In support of usercopy hardening, this patch defines a region
in the struct proto slab cache in which userspace copy operations are
allowed.

example usage trace:

    net/caif/caif_socket.c:
        setsockopt(...):
            ...
            copy_from_user(&cf_sk->conn_req.param.data, ..., ol)

This region is known as the slab cache's usercopy region. Slab caches
can now check that each dynamically sized copy operation involving
cache-managed memory falls entirely within the slab's usercopy region.

This patch is modified from Brad Spengler/PaX Team's PAX_USERCOPY
whitelisting code in the last public patch of grsecurity/PaX based on my
understanding of the code. Changes or omissions from the original code are
mine and don't reflect the original grsecurity/PaX code.

Signed-off-by: David Windsor <dave@nullcore.net>
[kees: split from network patch, provide usage trace]
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index 632d5a4..c76d513 100644 (file)
--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -1032,6 +1032,8 @@ static int caif_create(struct net *net, struct socket *sock, int protocol,
        static struct proto prot = {.name = "PF_CAIF",
                .owner = THIS_MODULE,
                .obj_size = sizeof(struct caifsock),
+               .useroffset = offsetof(struct caifsock, conn_req.param),
+               .usersize = sizeof_field(struct caifsock, conn_req.param)
        };
 
        if (!capable(CAP_SYS_ADMIN) && !capable(CAP_NET_ADMIN))