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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