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9339667c95For certain usecases, specifically where the sample interval is always set to a very low value such as 1ms, it can make sense to use a dynamic branch instead of static branches due to the overhead of toggling a static branch. Therefore, add a new Kconfig option to remove the static branches and instead check kfence_allocation_gate if a KFENCE allocation should be set up. Link: https://lkml.kernel.org/r/20210111091544.3287013-1-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Suggested-by: Jörn Engel <joern@purestorage.com> Reviewed-by: Jörn Engel <joern@purestorage.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Bug: 177201466 (cherry picked from commit c01761611b325c1e4ec7d3e236cc9db003cb82fd https://github.com/hnaz/linux-mm v5.11-rc4-mmots-2021-01-21-20-10) Test: CONFIG_KFENCE_KUNIT_TEST=y passes on Cuttlefish Signed-off-by: Alexander Potapenko <glider@google.com> Change-Id: I68a112a8ff68fa24742b198e036f130a9757c27f
67 lines
2.5 KiB
Text
67 lines
2.5 KiB
Text
# SPDX-License-Identifier: GPL-2.0-only
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config HAVE_ARCH_KFENCE
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bool
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menuconfig KFENCE
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bool "KFENCE: low-overhead sampling-based memory safety error detector"
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depends on HAVE_ARCH_KFENCE && !KASAN && (SLAB || SLUB)
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select STACKTRACE
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help
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KFENCE is a low-overhead sampling-based detector of heap out-of-bounds
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access, use-after-free, and invalid-free errors. KFENCE is designed
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to have negligible cost to permit enabling it in production
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environments.
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Note that, KFENCE is not a substitute for explicit testing with tools
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such as KASAN. KFENCE can detect a subset of bugs that KASAN can
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detect, albeit at very different performance profiles. If you can
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afford to use KASAN, continue using KASAN, for example in test
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environments. If your kernel targets production use, and cannot
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enable KASAN due to its cost, consider using KFENCE.
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if KFENCE
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config KFENCE_STATIC_KEYS
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bool "Use static keys to set up allocations"
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default y
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depends on JUMP_LABEL # To ensure performance, require jump labels
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help
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Use static keys (static branches) to set up KFENCE allocations. Using
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static keys is normally recommended, because it avoids a dynamic
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branch in the allocator's fast path. However, with very low sample
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intervals, or on systems that do not support jump labels, a dynamic
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branch may still be an acceptable performance trade-off.
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config KFENCE_SAMPLE_INTERVAL
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int "Default sample interval in milliseconds"
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default 100
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help
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The KFENCE sample interval determines the frequency with which heap
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allocations will be guarded by KFENCE. May be overridden via boot
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parameter "kfence.sample_interval".
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Set this to 0 to disable KFENCE by default, in which case only
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setting "kfence.sample_interval" to a non-zero value enables KFENCE.
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config KFENCE_NUM_OBJECTS
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int "Number of guarded objects available"
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range 1 65535
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default 255
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help
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The number of guarded objects available. For each KFENCE object, 2
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pages are required; with one containing the object and two adjacent
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ones used as guard pages.
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config KFENCE_STRESS_TEST_FAULTS
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int "Stress testing of fault handling and error reporting" if EXPERT
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default 0
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help
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The inverse probability with which to randomly protect KFENCE object
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pages, resulting in spurious use-after-frees. The main purpose of
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this option is to stress test KFENCE with concurrent error reports
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and allocations/frees. A value of 0 disables stress testing logic.
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Only for KFENCE testing; set to 0 if you are not a KFENCE developer.
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endif # KFENCE
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