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Date: Wed, 10 Jan 2018 18:02:57 -0800
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
	David Windsor <dave@...lcore.net>,
	"David S. Miller" <davem@...emloft.net>,
	netdev@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Christoph Lameter <cl@...ux.com>,
	Laura Abbott <labbott@...hat.com>,
	Mark Rutland <mark.rutland@....com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Dave Kleikamp <dave.kleikamp@...cle.com>,
	Jan Kara <jack@...e.cz>,
	Luis de Bethencourt <luisbg@...nel.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Rik van Riel <riel@...hat.com>,
	Matthew Garrett <mjg59@...gle.com>,
	linux-fsdevel@...r.kernel.org,
	linux-arch@...r.kernel.org,
	linux-mm@...ck.org,
	kernel-hardening@...ts.openwall.com
Subject: [PATCH 25/38] caif: Define usercopy region in caif proto slab cache

From: David Windsor <dave@...lcore.net>

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@...lcore.net>
[kees: split from network patch, provide usage trace]
Cc: "David S. Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 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

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