linux-kernel - [PATCH 37/38] usercopy: Restrict non-usercopy caches to size 0

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Date:   Wed, 10 Jan 2018 18:03:09 -0800
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        David Windsor <dave@...lcore.net>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        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,
        netdev@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: [PATCH 37/38] usercopy: Restrict non-usercopy caches to size 0

With all known usercopied cache whitelists now defined in the
kernel, switch the default usercopy region of kmem_cache_create()
to size 0. Any new caches with usercopy regions will now need to use
kmem_cache_create_usercopy() instead of kmem_cache_create().

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.

Cc: David Windsor <dave@...lcore.net>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 mm/slab_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 8ac2a6320a6c..d00cd3f0f8ac 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -532,7 +532,7 @@ struct kmem_cache *
 kmem_cache_create(const char *name, size_t size, size_t align,
 		slab_flags_t flags, void (*ctor)(void *))
 {
-	return kmem_cache_create_usercopy(name, size, align, flags, 0, size,
+	return kmem_cache_create_usercopy(name, size, align, flags, 0, 0,
 					  ctor);
 }
 EXPORT_SYMBOL(kmem_cache_create);
-- 
2.7.4