Commit 30c2c9f1 authored Jun 10, 2017 by David Windsor Committed by Kees Cook Jan 15, 2018

net: Define usercopy region in struct proto slab cache



In support of usercopy hardening, this patch defines a region in the
struct proto slab cache in which userspace copy operations are allowed.
Some protocols need to copy objects to/from userspace, and they can
declare the region via their proto structure with the new usersize and
useroffset fields. Initially, if no region is specified (usersize ==
0), the entire field is marked as whitelisted. This allows protocols
to be whitelisted in subsequent patches. Once all protocols have been
annotated, the full-whitelist default can be removed.

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: adjust commit log, split off per-proto patches]
[kees: add logic for by-default full-whitelist]
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

parent 0afe76e8

include/net/sock.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -1112,6 +1112,8 @@ struct proto {
		struct kmem_cache *slab;
		unsigned int obj_size;
		slab_flags_t slab_flags;
		size_t useroffset; /* Usercopy region offset */
		size_t usersize; /* Usercopy region size */

		struct percpu_counter *orphan_count;

net/core/sock.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -3151,8 +3151,12 @@ static int req_prot_init(const struct proto *prot)
		int proto_register(struct proto *prot, int alloc_slab)
		{
		if (alloc_slab) {
		prot->slab = kmem_cache_create(prot->name, prot->obj_size, 0,
		prot->slab = kmem_cache_create_usercopy(prot->name,
		prot->obj_size, 0,
		SLAB_HWCACHE_ALIGN \| prot->slab_flags,
		prot->usersize ? prot->useroffset : 0,
		prot->usersize ? prot->usersize
		: prot->obj_size,
		NULL);

		if (prot->slab == NULL) {

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