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kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS
This commit splits the current CONFIG_KASAN config option into two: 1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one that exists now); 2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode. The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have another hardware tag-based KASAN mode, that will rely on hardware memory tagging support in arm64. With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to instrument kernel files with -fsantize=kernel-hwaddress (except the ones for which KASAN_SANITIZE := n is set). Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes. This commit also adds empty placeholder (for now) implementation of tag-based KASAN specific hooks inserted by the compiler and adjusts common hooks implementation. While this commit adds the CONFIG_KASAN_SW_TAGS config option, this option is not selectable, as it depends on HAVE_ARCH_KASAN_SW_TAGS, which we will enable once all the infrastracture code has been added. Link: http://lkml.kernel.org/r/b2550106eb8a68b10fefbabce820910b115aa853.1544099024.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <[email protected]> Reviewed-by: Andrey Ryabinin <[email protected]> Reviewed-by: Dmitry Vyukov <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Mark Rutland <[email protected]> Cc: Will Deacon <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Andrey Konovalov
Linus Torvalds
parent
b938fcf427
commit
2bd926b439
11 changed files with 214 additions and 66 deletions
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@ -1,36 +1,92 @@
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# This config refers to the generic KASAN mode.
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config HAVE_ARCH_KASAN
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bool
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if HAVE_ARCH_KASAN
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config HAVE_ARCH_KASAN_SW_TAGS
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bool
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config CC_HAS_KASAN_GENERIC
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def_bool $(cc-option, -fsanitize=kernel-address)
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config CC_HAS_KASAN_SW_TAGS
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def_bool $(cc-option, -fsanitize=kernel-hwaddress)
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config KASAN
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bool "KASan: runtime memory debugger"
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bool "KASAN: runtime memory debugger"
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depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
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(HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)
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depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
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help
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Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
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designed to find out-of-bounds accesses and use-after-free bugs.
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See Documentation/dev-tools/kasan.rst for details.
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choice
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prompt "KASAN mode"
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depends on KASAN
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default KASAN_GENERIC
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help
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KASAN has two modes: generic KASAN (similar to userspace ASan,
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x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC) and
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software tag-based KASAN (a version based on software memory
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tagging, arm64 only, similar to userspace HWASan, enabled with
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CONFIG_KASAN_SW_TAGS).
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Both generic and tag-based KASAN are strictly debugging features.
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config KASAN_GENERIC
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bool "Generic mode"
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depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC
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depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
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select SLUB_DEBUG if SLUB
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select CONSTRUCTORS
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select STACKDEPOT
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help
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Enables kernel address sanitizer - runtime memory debugger,
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designed to find out-of-bounds accesses and use-after-free bugs.
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This is strictly a debugging feature and it requires a gcc version
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of 4.9.2 or later. Detection of out of bounds accesses to stack or
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global variables requires gcc 5.0 or later.
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This feature consumes about 1/8 of available memory and brings about
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~x3 performance slowdown.
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Enables generic KASAN mode.
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Supported in both GCC and Clang. With GCC it requires version 4.9.2
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or later for basic support and version 5.0 or later for detection of
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out-of-bounds accesses for stack and global variables and for inline
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instrumentation mode (CONFIG_KASAN_INLINE). With Clang it requires
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version 3.7.0 or later and it doesn't support detection of
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out-of-bounds accesses for global variables yet.
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This mode consumes about 1/8th of available memory at kernel start
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and introduces an overhead of ~x1.5 for the rest of the allocations.
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The performance slowdown is ~x3.
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For better error detection enable CONFIG_STACKTRACE.
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Currently CONFIG_KASAN doesn't work with CONFIG_DEBUG_SLAB
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Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB
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(the resulting kernel does not boot).
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config KASAN_EXTRA
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bool "KAsan: extra checks"
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depends on KASAN && DEBUG_KERNEL && !COMPILE_TEST
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config KASAN_SW_TAGS
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bool "Software tag-based mode"
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depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
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depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
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select SLUB_DEBUG if SLUB
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select CONSTRUCTORS
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select STACKDEPOT
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help
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This enables further checks in the kernel address sanitizer, for now
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it only includes the address-use-after-scope check that can lead
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to excessive kernel stack usage, frame size warnings and longer
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compile time.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 has more
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Enables software tag-based KASAN mode.
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This mode requires Top Byte Ignore support by the CPU and therefore
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is only supported for arm64.
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This mode requires Clang version 7.0.0 or later.
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This mode consumes about 1/16th of available memory at kernel start
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and introduces an overhead of ~20% for the rest of the allocations.
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This mode may potentially introduce problems relating to pointer
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casting and comparison, as it embeds tags into the top byte of each
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pointer.
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For better error detection enable CONFIG_STACKTRACE.
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Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB
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(the resulting kernel does not boot).
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endchoice
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config KASAN_EXTRA
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bool "KASAN: extra checks"
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depends on KASAN_GENERIC && DEBUG_KERNEL && !COMPILE_TEST
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help
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This enables further checks in generic KASAN, for now it only
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includes the address-use-after-scope check that can lead to
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excessive kernel stack usage, frame size warnings and longer
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compile time.
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See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715
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choice
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prompt "Instrumentation type"
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@ -53,7 +109,7 @@ config KASAN_INLINE
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memory accesses. This is faster than outline (in some workloads
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it gives about x2 boost over outline instrumentation), but
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make kernel's .text size much bigger.
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This requires a gcc version of 5.0 or later.
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For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later.
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endchoice
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@ -67,11 +123,9 @@ config KASAN_S390_4_LEVEL_PAGING
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4-level paging instead.
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config TEST_KASAN
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tristate "Module for testing kasan for bug detection"
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tristate "Module for testing KASAN for bug detection"
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depends on m && KASAN
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help
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This is a test module doing various nasty things like
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out of bounds accesses, use after free. It is useful for testing
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kernel debugging features like kernel address sanitizer.
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endif
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kernel debugging features like KASAN.
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