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[153/156] ubsan: introduce CONFIG_UBSAN_LOCAL_BOUNDS for Clang

Message ID 20201016025035.gAr-CGVi_%akpm@linux-foundation.org (mailing list archive)
State New
Headers show
Series [001/156] device-dax/kmem: fix resource release | expand

Commit Message

Andrew Morton Oct. 16, 2020, 2:50 a.m. UTC
From: George Popescu <georgepope@android.com>
Subject: ubsan: introduce CONFIG_UBSAN_LOCAL_BOUNDS for Clang

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

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

Link: https://lkml.kernel.org/r/20200922074330.2549523-1-georgepope@google.com
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>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

 lib/Kconfig.ubsan      |   14 ++++++++++++++
 scripts/Makefile.ubsan |   10 +++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)
diff mbox series


--- a/lib/Kconfig.ubsan~ubsan-introducing-config_ubsan_local_bounds-for-clang
+++ a/lib/Kconfig.ubsan
@@ -47,6 +47,20 @@  config UBSAN_BOUNDS
 	  to the {str,mem}*cpy() family of functions (that is addressed
+	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
--- a/scripts/Makefile.ubsan~ubsan-introducing-config_ubsan_local_bounds-for-clang
+++ a/scripts/Makefile.ubsan
@@ -4,7 +4,15 @@  ifdef CONFIG_UBSAN_ALIGNMENT
-      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
+      CFLAGS_UBSAN += -fsanitize=local-bounds