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Message-Id: <1450755641-7856-7-git-send-email-laura@labbott.name>
Date: Mon, 21 Dec 2015 19:40:40 -0800
From: Laura Abbott <laura@...bott.name>
To: 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>
Cc: Laura Abbott <laura@...bott.name>,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Kees Cook <keescook@...omium.org>,
kernel-hardening@...ts.openwall.com
Subject: [RFC][PATCH 6/7] mm: Add Kconfig option for slab sanitization
The SL[AOU]B allocators all behave differently w.r.t. to what happen
an object is freed. CONFIG_SLAB_SANITIZATION introduces a common
mechanism to control what happens on free. When this option is
enabled, objects may be poisoned according to a combination of
slab_sanitization command line option and whether SLAB_NO_SANITIZE
is set on a cache.
All credit for the original work should be given to Brad Spengler and
the PaX Team.
Signed-off-by: Laura Abbott <laura@...bott.name>
---
init/Kconfig | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/init/Kconfig b/init/Kconfig
index 235c7a2..37857f3 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1755,6 +1755,42 @@ config SLUB_CPU_PARTIAL
which requires the taking of locks that may cause latency spikes.
Typically one would choose no for a realtime system.
+config SLAB_MEMORY_SANITIZE
+ bool "Sanitize all freed memory"
+ help
+ By saying Y here the kernel will erase slab objects as soon as they
+ are freed. This in turn reduces the lifetime of data
+ stored in them, making it less likely that sensitive information such
+ as passwords, cryptographic secrets, etc stay in memory for too long.
+
+ This is especially useful for programs whose runtime is short, long
+ lived processes and the kernel itself benefit from this as long as
+ they ensure timely freeing of memory that may hold sensitive
+ information.
+
+ A nice side effect of the sanitization of slab objects is the
+ reduction of possible info leaks caused by padding bytes within the
+ leaky structures. Use-after-free bugs for structures containing
+ pointers can also be detected as dereferencing the sanitized pointer
+ will generate an access violation.
+
+ The tradeoff is performance impact. The noticible impact can vary
+ and you are advised to test this feature on your expected workload
+ before deploying it
+
+ The slab sanitization feature excludes a few slab caches per default
+ for performance reasons. The level of sanitization can be adjusted
+ with the sanitize_slab commandline option:
+ sanitize_slab=off: No sanitization will occur
+ santiize_slab=slow: Sanitization occurs only on the slow path
+ for all but the excluded slabs
+ (relevant for SLUB allocator only)
+ sanitize_slab=partial: Sanitization occurs on all path for all
+ but the excluded slabs
+ sanitize_slab=full: All slabs are sanitize
+
+ If unsure, say Y here.
+
config MMAP_ALLOW_UNINITIALIZED
bool "Allow mmapped anonymous memory to be uninitialized"
depends on EXPERT && !MMU
--
2.5.0
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