ubsan: Disable signed integer overflow sanitizer on GCC < 8

For opting functions out of sanitizer coverage, the "no_sanitize"
attribute is used, but in GCC this wasn't introduced until GCC 8.
Disable the sanitizer unless we're not using GCC, or it is GCC
version 8 or higher.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202403110643.27JXEVCI-lkp@intel.com/
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

ubsan: Reintroduce signed overflow sanitizer

In order to mitigate unexpected signed wrap-around[1], bring back the
signed integer overflow sanitizer. It was removed in commit 6aaa31aeb9cf
("ubsan: remove overflow checks") because it was effectively a no-op
when combined with -fno-strict-overflow (which correctly changes signed
overflow from being "undefined" to being explicitly "wrap around").

Compilers are adjusting their sanitizers to trap wrap-around and to
detecting common code patterns that should not be instrumented
(e.g. "var + offset < var"). Prepare for this and explicitly rename
the option from "OVERFLOW" to "WRAP" to more accurately describe the
behavior.

To annotate intentional wrap-around arithmetic, the helpers
wrapping_add/sub/mul_wrap() can be used for individual statements. At
the function level, the __signed_wrap attribute can be used to mark an
entire function as expecting its signed arithmetic to wrap around. For a
single object file the Makefile can use "UBSAN_SIGNED_WRAP_target.o := n"
to mark it as wrapping, and for an entire directory, "UBSAN_SIGNED_WRAP :=
n" can be used.

Additionally keep these disabled under CONFIG_COMPILE_TEST for now.

Link: https://github.com/KSPP/linux/issues/26 [1]
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hao Luo <haoluo@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

ubsan: Remove CONFIG_UBSAN_SANITIZE_ALL

For simplicity in splitting out UBSan options into separate rules,
remove CONFIG_UBSAN_SANITIZE_ALL, effectively defaulting to "y", which
is how it is generally used anyway. (There are no ":= y" cases beyond
where a specific file is enabled when a top-level ":= n" is in effect.)

Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: linux-doc@vger.kernel.org
Cc: linux-kbuild@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

ubsan: Clarify Kconfig text for CONFIG_UBSAN_TRAP

Make it clearer in the one-line description and the verbose description
text that CONFIG_UBSAN_TRAP as currently implemented involves a tradeoff of
much less helpful oops messages in exchange for a smaller kernel image.
(With the additional effect of turning UBSAN warnings into crashes, which
may or may not be desired.)

Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20230705215128.486054-1-jannh@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>

ubsan: remove cc-option test for UBSAN_TRAP

-fsanitize-undefined-trap-on-error has been supported since GCC 5.1 and
Clang 3.2. The minimum supported version of these according to
Documentation/process/changes.rst is 5.1 and 11.0.0 respectively. Drop
this cc-option check.

Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230407215406.768464-1-ndesaulniers@google.com

ubsan: Tighten UBSAN_BOUNDS on GCC

The use of -fsanitize=bounds on GCC will ignore some trailing arrays,
leaving a gap in coverage. Switch to using -fsanitize=bounds-strict to
match Clang's stricter behavior.

Cc: Marco Elver <elver@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Tom Rix <trix@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: linux-kbuild@vger.kernel.org
Cc: llvm@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230405022356.gonna.338-kees@kernel.org

ubsan: disable UBSAN_DIV_ZERO for clang

Building with UBSAN_DIV_ZERO with clang produces numerous fallthrough
warnings from objtool.

In the case of uncheck division, UBSAN_DIV_ZERO may introduce new
control flow to check for division by zero.

Because the result of the division is undefined, LLVM may optimize the
control flow such that after the call to __ubsan_handle_divrem_overflow
doesn't matter. If panic_on_warn was set,
__ubsan_handle_divrem_overflow would panic.

The problem is is that panic_on_warn is run time configurable. If it's
disabled, then we cannot guarantee that we will be able to recover
safely. Disable this config for clang until we can come up with a
solution in LLVM.

Link: https://github.com/ClangBuiltLinux/linux/issues/1657
Link: https://github.com/llvm/llvm-project/issues/56289
Link: https://lore.kernel.org/lkml/CAHk-=wj1qhf7y3VNACEexyp5EbkNpdcu_542k-xZpzmYLOjiCg@mail.gmail.com/
Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

objtool: Fix obsolete reference to CONFIG_X86_SMAP

CONFIG_X86_SMAP no longer exists. For objtool's purposes it has been
replaced with CONFIG_HAVE_UACCESS_VALIDATION.

Fixes: 03f16cd020eb ("objtool: Add CONFIG_OBJTOOL")
Reported-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/44c57668768c1ba1b4ba1ff541ec54781636e07c.1654101721.git.jpoimboe@kernel.org

objtool: Add CONFIG_OBJTOOL

Now that stack validation is an optional feature of objtool, add
CONFIG_OBJTOOL and replace most usages of CONFIG_STACK_VALIDATION with
it.

CONFIG_STACK_VALIDATION can now be considered to be frame-pointer
specific. CONFIG_UNWINDER_ORC is already inherently valid for live
patching, so no need to "validate" it.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/939bf3d85604b2a126412bf11af6e3bd3b872bcb.1650300597.git.jpoimboe@redhat.com

Revert "ubsan, kcsan: Don't combine sanitizer with kcov on clang"

This reverts commit ea91a1d45d19469001a4955583187b0d75915759.

Since df05c0e9496c ("Documentation: Raise the minimum supported version
of LLVM to 11.0.0") the minimum Clang version is now 11.0, which fixed
the UBSAN/KCSAN vs. KCOV incompatibilities.

Link: https://bugs.llvm.org/show_bug.cgi?id=45831
Link: https://lkml.kernel.org/r/YaodyZzu0MTCJcvO@elver.google.com
Link: https://lkml.kernel.org/r/20220128105631.509772-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: remove CONFIG_UBSAN_OBJECT_SIZE

The object-size sanitizer is redundant to -Warray-bounds, and
inappropriately performs its checks at run-time when all information
needed for the evaluation is available at compile-time, making it quite
difficult to use:

https://bugzilla.kernel.org/show_bug.cgi?id=214861

With -Warray-bounds almost enabled globally, it doesn't make sense to
keep this around.

Link: https://lkml.kernel.org/r/20211203235346.110809-1-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: remove overflow checks

Since GCC 8.0 -fsanitize=signed-integer-overflow doesn't work with
-fwrapv. -fwrapv makes signed overflows defines and GCC essentially
disables ubsan checks. On GCC < 8.0 -fwrapv doesn't have influence on
-fsanitize=signed-integer-overflow setting, so it kinda works but
generates false-positves and violates uaccess rules:

lib/iov_iter.o: warning: objtool: iovec_from_user()+0x22d: call to
__ubsan_handle_add_overflow() with UACCESS enabled

Disable signed overflow checks to avoid these problems. Remove unsigned
overflow checks as well. Unsigned overflow appeared as side effect of
commit cdf8a76fda4a ("ubsan: move cc-option tests into Kconfig"), but it
never worked (kernel doesn't boot). And unsigned overflows are allowed by
C standard, so it just pointless.

Link: https://lkml.kernel.org/r/20210209232348.20510-1-ryabinin.a.a@gmail.com
Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: disable unsigned-overflow check for i386

Building ubsan kernels even for compile-testing introduced these
warnings in my randconfig environment:

crypto/blake2b_generic.c:98:13: error: stack frame size of 9636 bytes in function 'blake2b_compress' [-Werror,-Wframe-larger-than=]
static void blake2b_compress(struct blake2b_state *S,

crypto/sha512_generic.c:151:13: error: stack frame size of 1292 bytes in function 'sha512_generic_block_fn' [-Werror,-Wframe-larger-than=]
static void sha512_generic_block_fn(struct sha512_state *sst, u8 const *src,

lib/crypto/curve25519-fiat32.c:312:22: error: stack frame size of 2180 bytes in function 'fe_mul_impl' [-Werror,-Wframe-larger-than=]
static noinline void fe_mul_impl(u32 out[10], const u32 in1[10], const u32 in2[10])

lib/crypto/curve25519-fiat32.c:444:22: error: stack frame size of 1588 bytes in function 'fe_sqr_impl' [-Werror,-Wframe-larger-than=]
static noinline void fe_sqr_impl(u32 out[10], const u32 in1[10])

Further testing showed that this is caused by
-fsanitize=unsigned-integer-overflow, but is isolated to the 32-bit x86
architecture.

The one in blake2b immediately overflows the 8KB stack area
architectures, so better ensure this never happens by disabling the
option for 32-bit x86.

Link: https://lkml.kernel.org/r/20210112202922.2454435-1-arnd@kernel.org
Link: https://lore.kernel.org/lkml/20201230154749.746641-1-arnd@kernel.org/
Fixes: d0a3ac549f38 ("ubsan: enable for all*config builds")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Marco Elver <elver@google.com>
Cc: George Popescu <georgepope@android.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: remove UBSAN_MISC in favor of individual options

Make each UBSAN option individually selectable and remove UBSAN_MISC which
no longer has any purpose. Add help text for each Kconfig, and include a
reference to the Clang sanitizer documentation. Disable unsigned overflow
by default (not available with GCC and makes x86 unbootable with Clang).
Disable unreachable when objtool is in use (redundant and confuses things:
instrumentation appears at unreachable locations).

Link: https://lkml.kernel.org/r/20201203004437.389959-7-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: George Popescu <georgepope@android.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Marco Elver <elver@google.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: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: enable for all*config builds

With UBSAN_OBJECT_SIZE disabled for GCC, only UBSAN_ALIGNMENT remained a
noisy UBSAN option. Disable it for COMPILE_TEST so the rest of UBSAN can
be used for full all*config builds or other large combinations.

[sfr@canb.auug.org.au: add .data..Lubsan_data*/.data..Lubsan_type* sections explicitly]
Link: https://lkml.kernel.org/r/20201208230157.42c42789@canb.auug.org.au

Link: https://lore.kernel.org/lkml/CAHk-=wgXW=YLxGN0QVpp-1w5GDd2pf1W-FqY15poKzoVfik2qA@mail.gmail.com/
Link: https://lkml.kernel.org/r/20201203004437.389959-6-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: George Popescu <georgepope@android.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Marco Elver <elver@google.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: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: disable UBSAN_TRAP for all*config

Doing all*config builds attempts to build as much as possible. UBSAN_TRAP
effectively short-circuits lib/usban.c, so it should be disabled for
COMPILE_TEST so that the lib/ubsan.c code gets built.

Link: https://lkml.kernel.org/r/20201203004437.389959-5-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: George Popescu <georgepope@android.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Marco Elver <elver@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: disable object-size sanitizer under GCC

GCC's -fsanitize=object-size (as part of CONFIG_UBSAN_MISC) greatly
increases stack utilization. Do not allow this under GCC.

Link: https://lkml.kernel.org/r/20201203004437.389959-4-keescook@chromium.org
Link: https://lore.kernel.org/lkml/CAHk-=wjPasyJrDuwDnpHJS2TuQfExwe=px-SzLeN8GFMAQJPmQ@mail.gmail.com/
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: George Popescu <georgepope@android.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Marco Elver <elver@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: move cc-option tests into Kconfig

Instead of doing if/endif blocks with cc-option calls in the UBSAN
Makefile, move all the tests into Kconfig and use the Makefile to collect
the results.

Link: https://lkml.kernel.org/r/20201203004437.389959-3-keescook@chromium.org
Link: https://lore.kernel.org/lkml/CAHk-=wjPasyJrDuwDnpHJS2TuQfExwe=px-SzLeN8GFMAQJPmQ@mail.gmail.com/
Signed-off-by: Kees Cook <keescook@chromium.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: George Popescu <georgepope@android.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Marco Elver <elver@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: remove redundant -Wno-maybe-uninitialized

Patch series "Clean up UBSAN Makefile", v2.

This series attempts to address the issues seen with UBSAN's object-size
sanitizer causing problems under GCC. In the process, the Kconfig and
Makefile are refactored to do all the cc-option calls in the Kconfig.
Additionally start to detangle -Wno-maybe-uninitialized, disable
UBSAN_TRAP under COMPILE_TEST for wider build coverage, and expand the
libusan tests.

This patch (of 7):

In commit 78a5255ffb6a ("Stop the ad-hoc games with
-Wno-maybe-initialized") -Wmaybe-uninitialized was disabled globally, so
keeping the disabling logic here too doesn't make sense.

Link: https://lkml.kernel.org/r/20201203004437.389959-1-keescook@chromium.org
Link: https://lkml.kernel.org/r/20201203004437.389959-2-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
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: Marco Elver <elver@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: George Popescu <georgepope@android.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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
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>
Signed-off-by: George Popescu <georgepope@android.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Brazdil <dbrazdil@google.com>
Reviewed-by: Marco Elver <elver@google.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>
Link: https://lkml.kernel.org/r/20200922074330.2549523-1-georgepope@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan, kcsan: Don't combine sanitizer with kcov on clang

Clang does not allow -fsanitize-coverage=trace-{pc,cmp} together
with -fsanitize=bounds or with ubsan:

clang: error: argument unused during compilation: '-fsanitize-coverage=trace-pc' [-Werror,-Wunused-command-line-argument]
clang: error: argument unused during compilation: '-fsanitize-coverage=trace-cmp' [-Werror,-Wunused-command-line-argument]

To avoid the warning, check whether clang can handle this correctly or
disallow ubsan and kcsan when kcov is enabled.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marco Elver <elver@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://bugs.llvm.org/show_bug.cgi?id=45831
Link: https://lore.kernel.org/lkml/20200505142341.1096942-1-arnd@arndb.de
Link: https://lkml.kernel.org/r/20200521142047.169334-2-elver@google.com

ubsan: entirely disable alignment checks under UBSAN_TRAP

Commit 8d58f222e85f ("ubsan: disable UBSAN_ALIGNMENT under
COMPILE_TEST") tried to fix the pathological results of UBSAN_ALIGNMENT
with UBSAN_TRAP (which objtool would rightly scream about), but it made
an assumption about how COMPILE_TEST gets set (it is not set for
randconfig). As a result, we need a bigger hammer here: just don't
allow the alignment checks with the trap mode.

Fixes: 8d58f222e85f ("ubsan: disable UBSAN_ALIGNMENT under COMPILE_TEST")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Elena Petrova <lenaptr@google.com>
Link: http://lkml.kernel.org/r/202005291236.000FCB6@keescook
Link: https://lore.kernel.org/lkml/742521db-1e8c-0d7a-1ed4-a908894fb497@infradead.org/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: disable UBSAN_ALIGNMENT under COMPILE_TEST

The documentation for UBSAN_ALIGNMENT already mentions that it should
not be used on all*config builds (and for efficient-unaligned-access
architectures), so just refactor the Kconfig to correctly implement this
so randconfigs will stop creating insane images that freak out objtool
under CONFIG_UBSAN_TRAP (due to the false positives producing functions
that never return, etc).

Link: http://lkml.kernel.org/r/202005011433.C42EA3E2D@keescook
Fixes: 0887a7ebc977 ("ubsan: add trap instrumentation option")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/linux-next/202004231224.D6B3B650@keescook/
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: split "bounds" checker from other options

In order to do kernel builds with the bounds checker individually
available, introduce CONFIG_UBSAN_BOUNDS, with the remaining options under
CONFIG_UBSAN_MISC.

For example, using this, we can start to expand the coverage syzkaller is
providing. Right now, all of UBSan is disabled for syzbot builds because
taken as a whole, it is too noisy. This will let us focus on one feature
at a time.

For the bounds checker specifically, this provides a mechanism to
eliminate an entire class of array overflows with close to zero
performance overhead (I cannot measure a difference). In my (mostly)
defconfig, enabling bounds checking adds ~4200 checks to the kernel.
Performance changes are in the noise, likely due to the branch predictors
optimizing for the non-fail path.

Some notes on the bounds checker:

- it does not instrument {mem,str}*()-family functions, it only
instruments direct indexed accesses (e.g. "foo[i]"). Dealing with
the {mem,str}*()-family functions is a work-in-progress around
CONFIG_FORTIFY_SOURCE[1].

- it ignores flexible array members, including the very old single
byte (e.g. "int foo[1];") declarations. (Note that GCC's
implementation appears to ignore _all_ trailing arrays, but Clang only
ignores empty, 0, and 1 byte arrays[2].)

[1] https://github.com/KSPP/linux/issues/6
[2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92589

Suggested-by: Elena Petrova <lenaptr@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Link: http://lkml.kernel.org/r/20200227193516.32566-3-keescook@chromium.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: add trap instrumentation option

Patch series "ubsan: Split out bounds checker", v5.

This splits out the bounds checker so it can be individually used. This
is enabled in Android and hopefully for syzbot. Includes LKDTM tests for
behavioral corner-cases (beyond just the bounds checker), and adjusts
ubsan and kasan slightly for correct panic handling.

This patch (of 6):

The Undefined Behavior Sanitizer can operate in two modes: warning
reporting mode via lib/ubsan.c handler calls, or trap mode, which uses
__builtin_trap() as the handler. Using lib/ubsan.c means the kernel image
is about 5% larger (due to all the debugging text and reporting structures
to capture details about the warning conditions). Using the trap mode,
the image size changes are much smaller, though at the loss of the
"warning only" mode.

In order to give greater flexibility to system builders that want minimal
changes to image size and are prepared to deal with kernel code being
aborted and potentially destabilizing the system, this introduces
CONFIG_UBSAN_TRAP. The resulting image sizes comparison:

text data bss dec hex filename
19533663 6183037 18554956 44271656 2a38828 vmlinux.stock
19991849 7618513 18874448 46484810 2c54d4a vmlinux.ubsan
19712181 6284181 18366540 44362902 2a4ec96 vmlinux.ubsan-trap

CONFIG_UBSAN=y: image +4.8% (text +2.3%, data +18.9%)
CONFIG_UBSAN_TRAP=y: image +0.2% (text +0.9%, data +1.6%)

Additionally adjusts the CONFIG_UBSAN Kconfig help for clarity and removes
the mention of non-existing boot param "ubsan_handle".

Suggested-by: Elena Petrova <lenaptr@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Link: http://lkml.kernel.org/r/20200227193516.32566-2-keescook@chromium.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

lib/ubsan: default UBSAN_ALIGNMENT to not set

When booting an allmodconfig kernel, there are a lot of false-positives.
With a message like this 'UBSAN: Undefined behaviour in...' with a call
trace that follows.

UBSAN warnings are a result of enabling noisy CONFIG_UBSAN_ALIGNMENT
which is disabled by default if HAVE_EFFICIENT_UNALIGNED_ACCESS=y.

It's noisy even if don't have efficient unaligned access, e.g. people
often add __cacheline_aligned_in_smp in structs, but forget to align
allocations of such struct (kmalloc() give 8-byte alignment in worst
case).

Rework so that when building a allmodconfig kernel that turns everything
into '=m' or '=y' will turn off UBSAN_ALIGNMENT.

[aryabinin@virtuozzo.com: changelog addition]
Link: http://lkml.kernel.org/r/20181217150326.30933-1-anders.roxell@linaro.org
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/ubsan: remove null-pointer checks

With gcc-8 fsanitize=null become very noisy. GCC started to complain
about things like &a->b, where 'a' is NULL pointer. There is no NULL
dereference, we just calculate address to struct member. It's
technically undefined behavior so UBSAN is correct to report it. But as
long as there is no real NULL-dereference, I think, we should be fine.

-fno-delete-null-pointer-checks compiler flag should protect us from any
consequences. So let's just no use -fsanitize=null as it's not useful
for us. If there is a real NULL-deref we will see crash. Even if
userspace mapped something at NULL (root can do this), with things like
SMAP should catch the issue.

Link: http://lkml.kernel.org/r/20180802153209.813-1-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib: add testing module for UBSAN

This is a test module for UBSAN. It triggers all undefined behaviors
that linux supports now, and detect them.

All test-cases have passed by compiling with gcc-5.5.0.

If use gcc-4.9.x, misaligned, out-of-bounds, object-size-mismatch will not
be detected. Because gcc-4.9.x doesn't support them.

Link: http://lkml.kernel.org/r/20180309102247.GA2944@pjb1027-Latitude-E5410
Signed-off-by: Jinbum Park <jinb.park7@gmail.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Kconfig: lib/Kconfig.ubsan fix reference to ubsan documentation

Documenation/ubsan.txt was moved to Documentation/dev-tools/ubsan.rst,
this fixes the reference.

Link: http://lkml.kernel.org/r/1476698152-29340-3-git-send-email-andreas.platschek@opentech.at
Signed-off-by: Andreas Platschek <andreas.platschek@opentech.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: allow to disable the null sanitizer

Some architectures use a hardware defined structure at address zero.
Checking for a null pointer will result in many ubsan reports.
Allow users to disable the null sanitizer.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

ubsan: fix tree-wide -Wmaybe-uninitialized false positives

-fsanitize=* options makes GCC less smart than usual and increase number
of 'maybe-uninitialized' false-positives. So this patch does two things:

* Add -Wno-maybe-uninitialized to CFLAGS_UBSAN which will disable all
such warnings for instrumented files.

* Remove CONFIG_UBSAN_SANITIZE_ALL from all[yes|mod]config builds. So
the all[yes|mod]config build goes without -fsanitize=* and still with
-Wmaybe-uninitialized.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ubsan: cosmetic fix to Kconfig text

When enabling UBSAN_SANITIZE_ALL, the kernel image size gets increased
significantly (~3x). So, it sounds better to have some note in Kconfig.

And, fixed a typo.

Signed-off-by: Yang Shi <yang.shi@linaro.org>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

UBSAN: run-time undefined behavior sanity checker

UBSAN uses compile-time instrumentation to catch undefined behavior
(UB). Compiler inserts code that perform certain kinds of checks before
operations that could cause UB. If check fails (i.e. UB detected)
__ubsan_handle_* function called to print error message.

So the most of the work is done by compiler. This patch just implements
ubsan handlers printing errors.

GCC has this capability since 4.9.x [1] (see -fsanitize=undefined
option and its suboptions).
However GCC 5.x has more checkers implemented [2].
Article [3] has a bit more details about UBSAN in the GCC.

[1] - https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Debugging-Options.html
[2] - https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html
[3] - http://developerblog.redhat.com/2014/10/16/gcc-undefined-behavior-sanitizer-ubsan/

Issues which UBSAN has found thus far are:

Found bugs:

* out-of-bounds access - 97840cb67ff5 ("netfilter: nfnetlink: fix
insufficient validation in nfnetlink_bind")

undefined shifts:

* d48458d4a768 ("jbd2: use a better hash function for the revoke
table")

* 10632008b9e1 ("clockevents: Prevent shift out of bounds")

* 'x << -1' shift in ext4 -
http://lkml.kernel.org/r/<5444EF21.8020501@samsung.com>

* undefined rol32(0) -
http://lkml.kernel.org/r/<1449198241-20654-1-git-send-email-sasha.levin@oracle.com>

* undefined dirty_ratelimit calculation -
http://lkml.kernel.org/r/<566594E2.3050306@odin.com>

* undefined roundown_pow_of_two(0) -
http://lkml.kernel.org/r/<1449156616-11474-1-git-send-email-sasha.levin@oracle.com>

* [WONTFIX] undefined shift in __bpf_prog_run -
http://lkml.kernel.org/r/<CACT4Y+ZxoR3UjLgcNdUm4fECLMx2VdtfrENMtRRCdgHB2n0bJA@mail.gmail.com>

WONTFIX here because it should be fixed in bpf program, not in kernel.

signed overflows:

* 32a8df4e0b33f ("sched: Fix odd values in effective_load()
calculations")

* mul overflow in ntp -
http://lkml.kernel.org/r/<1449175608-1146-1-git-send-email-sasha.levin@oracle.com>

* incorrect conversion into rtc_time in rtc_time64_to_tm() -
http://lkml.kernel.org/r/<1449187944-11730-1-git-send-email-sasha.levin@oracle.com>

* unvalidated timespec in io_getevents() -
http://lkml.kernel.org/r/<CACT4Y+bBxVYLQ6LtOKrKtnLthqLHcw-BMp3aqP3mjdAvr9FULQ@mail.gmail.com>

* [NOTABUG] signed overflow in ktime_add_safe() -
http://lkml.kernel.org/r/<CACT4Y+aJ4muRnWxsUe1CMnA6P8nooO33kwG-c8YZg=0Xc8rJqw@mail.gmail.com>

[akpm@linux-foundation.org: fix unused local warning]
[akpm@linux-foundation.org: fix __int128 build woes]
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Yury Gribov <y.gribov@samsung.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>