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net: Define usercopy region in struct proto slab cache

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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>
This commit is contained in:
David Windsor 2017-06-10 22:50:42 -04:00 committed by Kees Cook
parent 0afe76e88c
commit 30c2c9f158
2 changed files with 7 additions and 1 deletions
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2
include/net/sock.h
View File

@ -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;

6
net/core/sock.c
View File

@ -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) {