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Message-Id: <1469046427-12696-13-git-send-email-keescook@chromium.org>
Date: Wed, 20 Jul 2016 13:27:07 -0700
From: Kees Cook <keescook@...omium.org>
To: kernel-hardening@...ts.openwall.com
Cc: Kees Cook <keescook@...omium.org>,
Laura Abbott <labbott@...oraproject.org>,
Balbir Singh <bsingharora@...il.com>,
Daniel Micay <danielmicay@...il.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
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>,
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,
linux-kernel@...r.kernel.org
Subject: [PATCH v4 12/12] mm: SLUB hardened usercopy support
Under CONFIG_HARDENED_USERCOPY, this adds object size checking to the
SLUB allocator to catch any copies that may span objects. Includes a
redzone handling fix discovered by Michael Ellerman.
Based on code from PaX and grsecurity.
Signed-off-by: Kees Cook <keescook@...omium.org>
Tested-by: Michael Ellerman <mpe@...erman.id.au>
---
init/Kconfig | 1 +
mm/slub.c | 36 ++++++++++++++++++++++++++++++++++++
2 files changed, 37 insertions(+)
diff --git a/init/Kconfig b/init/Kconfig
index 798c2020ee7c..1c4711819dfd 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1765,6 +1765,7 @@ config SLAB
config SLUB
bool "SLUB (Unqueued Allocator)"
+ select HAVE_HARDENED_USERCOPY_ALLOCATOR
help
SLUB is a slab allocator that minimizes cache line usage
instead of managing queues of cached objects (SLAB approach).
diff --git a/mm/slub.c b/mm/slub.c
index 825ff4505336..7dee3d9a5843 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3614,6 +3614,42 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node)
EXPORT_SYMBOL(__kmalloc_node);
#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 *s;
+ unsigned long offset;
+ size_t object_size;
+
+ /* Find object and usable object size. */
+ s = page->slab_cache;
+ object_size = slab_ksize(s);
+
+ /* Find offset within object. */
+ offset = (ptr - page_address(page)) % s->size;
+
+ /* Adjust for redzone and reject if within the redzone. */
+ if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE) {
+ if (offset < s->red_left_pad)
+ return s->name;
+ offset -= s->red_left_pad;
+ }
+
+ /* Allow address range falling entirely within object size. */
+ if (offset <= object_size && n <= object_size - offset)
+ return NULL;
+
+ return s->name;
+}
+#endif /* CONFIG_HARDENED_USERCOPY */
+
static size_t __ksize(const void *object)
{
struct page *page;
--
2.7.4
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