From: Qian Cai <cai@redhat.com>
To: Marco Elver <elver@google.com>,
akpm@linux-foundation.org, glider@google.com
Cc: mark.rutland@arm.com, linux-doc@vger.kernel.org,
peterz@infradead.org, catalin.marinas@arm.com,
dave.hansen@linux.intel.com, linux-mm@kvack.org,
edumazet@google.com, hpa@zytor.com, cl@linux.com,
will@kernel.org, corbet@lwn.net, x86@kernel.org,
kasan-dev@googlegroups.com, mingo@redhat.com, vbabka@suse.cz,
rientjes@google.com, aryabinin@virtuozzo.com,
keescook@chromium.org, paulmck@kernel.org, jannh@google.com,
andreyknvl@google.com, bp@alien8.de, luto@kernel.org,
Jonathan.Cameron@huawei.com, tglx@linutronix.de,
dvyukov@google.com, linux-arm-kernel@lists.infradead.org,
gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
penberg@kernel.org, iamjoonsoo.kim@lge.com
Subject: Re: [PATCH v2 00/10] KFENCE: A low-overhead sampling-based memory safety error detector
Date: Fri, 18 Sep 2020 07:17:06 -0400 [thread overview]
Message-ID: <115e74b249417340b5c411f286768dbdb916fd12.camel@redhat.com> (raw)
In-Reply-To: <20200915132046.3332537-1-elver@google.com>
On Tue, 2020-09-15 at 15:20 +0200, Marco Elver wrote:
> This adds the Kernel Electric-Fence (KFENCE) infrastructure. KFENCE is a
> low-overhead sampling-based memory safety error detector of heap
> use-after-free, invalid-free, and out-of-bounds access errors. This
> series enables KFENCE for the x86 and arm64 architectures, and adds
> KFENCE hooks to the SLAB and SLUB allocators.
>
> KFENCE is designed to be enabled in production kernels, and has near
> zero performance overhead. Compared to KASAN, KFENCE trades performance
> for precision. The main motivation behind KFENCE's design, is that with
> enough total uptime KFENCE will detect bugs in code paths not typically
> exercised by non-production test workloads. One way to quickly achieve a
> large enough total uptime is when the tool is deployed across a large
> fleet of machines.
>
> KFENCE objects each reside on a dedicated page, at either the left or
> right page boundaries. The pages to the left and right of the object
> page are "guard pages", whose attributes are changed to a protected
> state, and cause page faults on any attempted access to them. Such page
> faults are then intercepted by KFENCE, which handles the fault
> gracefully by reporting a memory access error.
>
> Guarded allocations are set up based on a sample interval (can be set
> via kfence.sample_interval). After expiration of the sample interval,
> the next allocation through the main allocator (SLAB or SLUB) returns a
> guarded allocation from the KFENCE object pool. At this point, the timer
> is reset, and the next allocation is set up after the expiration of the
> interval.
>
> To enable/disable a KFENCE allocation through the main allocator's
> fast-path without overhead, KFENCE relies on static branches via the
> static keys infrastructure. The static branch is toggled to redirect the
> allocation to KFENCE.
>
> The KFENCE memory pool is of fixed size, and if the pool is exhausted no
> further KFENCE allocations occur. The default config is conservative
> with only 255 objects, resulting in a pool size of 2 MiB (with 4 KiB
> pages).
>
> We have verified by running synthetic benchmarks (sysbench I/O,
> hackbench) that a kernel with KFENCE is performance-neutral compared to
> a non-KFENCE baseline kernel.
>
> KFENCE is inspired by GWP-ASan [1], a userspace tool with similar
> properties. The name "KFENCE" is a homage to the Electric Fence Malloc
> Debugger [2].
>
> For more details, see Documentation/dev-tools/kfence.rst added in the
> series -- also viewable here:
Does anybody else grow tried of all those different *imperfect* versions of in-
kernel memory safety error detectors? KASAN-generic, KFENCE, KASAN-tag-based
etc. Then, we have old things like page_poison, SLUB debugging, debug_pagealloc
etc which are pretty much inefficient to detect bugs those days compared to
KASAN. Can't we work towards having a single implementation and clean up all
those mess?
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next prev parent reply other threads:[~2020-09-18 11:18 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 13:20 [PATCH v2 00/10] KFENCE: A low-overhead sampling-based memory safety error detector Marco Elver
2020-09-15 13:20 ` [PATCH v2 01/10] mm: add Kernel Electric-Fence infrastructure Marco Elver
2020-09-17 13:26 ` Hillf Danton
2020-09-17 13:36 ` Marco Elver
2020-09-17 23:45 ` Hillf Danton
2020-09-15 13:20 ` [PATCH v2 02/10] x86, kfence: enable KFENCE for x86 Marco Elver
2020-09-15 13:20 ` [PATCH v2 03/10] arm64, kfence: enable KFENCE for ARM64 Marco Elver
2020-09-15 13:20 ` [PATCH v2 04/10] mm, kfence: insert KFENCE hooks for SLAB Marco Elver
2020-09-17 9:37 ` Christopher Lameter
2020-09-17 9:47 ` Alexander Potapenko
2020-09-15 13:20 ` [PATCH v2 05/10] mm, kfence: insert KFENCE hooks for SLUB Marco Elver
2020-09-17 9:40 ` Christopher Lameter
2020-09-17 9:51 ` Alexander Potapenko
2020-09-15 13:20 ` [PATCH v2 06/10] kfence, kasan: make KFENCE compatible with KASAN Marco Elver
2020-09-15 13:20 ` [PATCH v2 07/10] kfence, kmemleak: make KFENCE compatible with KMEMLEAK Marco Elver
2020-09-15 13:20 ` [PATCH v2 08/10] kfence, lockdep: make KFENCE compatible with lockdep Marco Elver
2020-09-15 13:20 ` [PATCH v2 09/10] kfence, Documentation: add KFENCE documentation Marco Elver
2020-09-15 13:20 ` [PATCH v2 10/10] kfence: add test suite Marco Elver
2020-09-15 13:49 ` [PATCH v2 00/10] KFENCE: A low-overhead sampling-based memory safety error detector Dmitry Vyukov
2020-09-18 11:17 ` Qian Cai [this message]
2020-09-18 11:59 ` Marco Elver
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