# \[PATCH v2 20/30\] caif: Define usercopy region in caif proto slab cache

- Subsystems: NETWORKING \[GENERAL\], THE REST
- Maintainers: "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
- Status: SUPERSEDED (Superseded by v5 posted 2018-01-11)
- Superseded by v5 (posted 2018-01-11).
- Revision v2 (5 revisions archived).
- List: netdev
- 1 message, 1 author
- Page: https://ratatoskr.run/netdev/2017/08/5077692/t

## \[PATCH v2 20/30\] caif: Define usercopy region in caif proto slab cache

- From: Kees Cook \<hidden\>
- Date: 2017-08-28 21:36:01 
- Message: https://ratatoskr.run/netdev/2017/08/5077692.md

```text
From: David Windsor <redacted>

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 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 <redacted>
[kees: split from network patch, provide usage trace]
Cc: Dmitry Tarnyagin <redacted>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: <redacted>
Signed-off-by: Kees Cook <redacted>
---
 net/caif/caif_socket.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index 632d5a416d97..c76d513b9a7a 100644
--- 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))
-- 
2.7.4
```