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Message-Id: <1467843928-29351-9-git-send-email-keescook@chromium.org>
Date: Wed, 6 Jul 2016 15:25:27 -0700
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
Rik van Riel <riel@...hat.com>,
Casey Schaufler <casey@...aufler-ca.com>,
PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>,
Russell King <linux@...linux.org.uk>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Michael Ellerman <mpe@...erman.id.au>,
Tony Luck <tony.luck@...el.com>,
Fenghua Yu <fenghua.yu@...el.com>,
"David S. Miller" <davem@...emloft.net>,
x86@...nel.org,
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>,
Andy Lutomirski <luto@...nel.org>,
Borislav Petkov <bp@...e.de>,
Mathias Krause <minipli@...glemail.com>,
Jan Kara <jack@...e.cz>,
Vitaly Wool <vitalywool@...il.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Laura Abbott <labbott@...oraproject.org>,
linux-arm-kernel@...ts.infradead.org,
linux-ia64@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org,
sparclinux@...r.kernel.org,
linux-arch@...r.kernel.org,
linux-mm@...ck.org,
kernel-hardening@...ts.openwall.com
Subject: [PATCH 8/9] mm: SLAB hardened usercopy support
Under CONFIG_HARDENED_USERCOPY, this adds object size checking to the
SLAB allocator to catch any copies that may span objects.
Based on code from PaX and grsecurity.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
init/Kconfig | 1 +
mm/slab.c | 30 ++++++++++++++++++++++++++++++
2 files changed, 31 insertions(+)
diff --git a/init/Kconfig b/init/Kconfig
index f755a602d4a1..798c2020ee7c 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1757,6 +1757,7 @@ choice
config SLAB
bool "SLAB"
+ select HAVE_HARDENED_USERCOPY_ALLOCATOR
help
The regular slab allocator that is established and known to work
well in all environments. It organizes cache hot objects in
diff --git a/mm/slab.c b/mm/slab.c
index cc8bbc1e6bc9..5e2d5f349aca 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4477,6 +4477,36 @@ static int __init slab_proc_init(void)
module_init(slab_proc_init);
#endif
+#ifdef CONFIG_HARDENED_USERCOPY
+/*
+ * Rejects objects that are incorrectly sized.
+ *
+ * Returns NULL if check passes, otherwise const char * to name of cache
+ * to indicate an error.
+ */
+const char *__check_heap_object(const void *ptr, unsigned long n,
+ struct page *page)
+{
+ struct kmem_cache *cachep;
+ unsigned int objnr;
+ unsigned long offset;
+
+ /* Find and validate object. */
+ cachep = page->slab_cache;
+ objnr = obj_to_index(cachep, page, (void *)ptr);
+ BUG_ON(objnr >= cachep->num);
+
+ /* Find offset within object. */
+ offset = ptr - index_to_obj(cachep, page, objnr) - obj_offset(cachep);
+
+ /* Allow address range falling entirely within object size. */
+ if (offset <= cachep->object_size && n <= cachep->object_size - offset)
+ return NULL;
+
+ return cachep->name;
+}
+#endif /* CONFIG_HARDENED_USERCOPY */
+
/**
* ksize - get the actual amount of memory allocated for a given object
* @objp: Pointer to the object
--
2.7.4
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