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SubjectRe: [PATCH v3] ubsan: introducing CONFIG_UBSAN_LOCAL_BOUNDS for Clang
Is this patch ready to be merged?

Best regards,
George


On Tue, Sep 22, 2020 at 10:43 AM George-Aurelian Popescu
<georgepope@google.com> wrote:
>
> From: George Popescu <georgepope@android.com>
>
> When the kernel is compiled with Clang, -fsanitize=bounds expands to
> -fsanitize=array-bounds and -fsanitize=local-bounds.
>
> Enabling -fsanitize=local-bounds with Clang has the unfortunate
> side-effect of inserting traps; this goes back to its original intent,
> which was as a hardening and not a debugging feature [1]. The same feature
> made its way into -fsanitize=bounds, but the traps remained. For that
> reason, -fsanitize=bounds was split into 'array-bounds' and
> 'local-bounds' [2].
>
> Since 'local-bounds' doesn't behave like a normal sanitizer, enable
> it with Clang only if trapping behaviour was requested by
> CONFIG_UBSAN_TRAP=y.
>
> Add the UBSAN_BOUNDS_LOCAL config to Kconfig.ubsan to enable the
> 'local-bounds' option by default when UBSAN_TRAP is enabled.
>
> [1] http://lists.llvm.org/pipermail/llvm-dev/2012-May/049972.html
> [2] http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20131021/091536.html
>
> Suggested-by: Marco Elver <elver@google.com>
> Reviewed-by: David Brazdil <dbrazdil@google.com>
> Reviewed-by: Marco Elver <elver@google.com>
> Signed-off-by: George Popescu <georgepope@android.com>
>
> ---
> v2: changed the name of the config, in Kconfig, to UBSAN_LOCAL_BOUNDS
> ---
> v3: added Reviewed-by tag
> ---
> lib/Kconfig.ubsan | 14 ++++++++++++++
> scripts/Makefile.ubsan | 10 +++++++++-
> 2 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
> index 774315de555a..58f8d03d037b 100644
> --- a/lib/Kconfig.ubsan
> +++ b/lib/Kconfig.ubsan
> @@ -47,6 +47,20 @@ config UBSAN_BOUNDS
> to the {str,mem}*cpy() family of functions (that is addressed
> by CONFIG_FORTIFY_SOURCE).
>
> +config UBSAN_LOCAL_BOUNDS
> + bool "Perform array local bounds checking"
> + depends on UBSAN_TRAP
> + depends on CC_IS_CLANG
> + depends on !UBSAN_KCOV_BROKEN
> + help
> + This option enables -fsanitize=local-bounds which traps when an
> + exception/error is detected. Therefore, it should be enabled only
> + if trapping is expected.
> + Enabling this option detects errors due to accesses through a
> + pointer that is derived from an object of a statically-known size,
> + where an added offset (which may not be known statically) is
> + out-of-bounds.
> +
> config UBSAN_MISC
> bool "Enable all other Undefined Behavior sanity checks"
> default UBSAN
> diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
> index 27348029b2b8..4e3fff0745e8 100644
> --- a/scripts/Makefile.ubsan
> +++ b/scripts/Makefile.ubsan
> @@ -4,7 +4,15 @@ ifdef CONFIG_UBSAN_ALIGNMENT
> endif
>
> ifdef CONFIG_UBSAN_BOUNDS
> - CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
> + ifdef CONFIG_CC_IS_CLANG
> + CFLAGS_UBSAN += -fsanitize=array-bounds
> + else
> + CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
> + endif
> +endif
> +
> +ifdef CONFIG_UBSAN_LOCAL_BOUNDS
> + CFLAGS_UBSAN += -fsanitize=local-bounds
> endif
>
> ifdef CONFIG_UBSAN_MISC
> --
> 2.28.0.681.g6f77f65b4e-goog
>

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