Commit 3ca17b1f authored by Andrey Ryabinin's avatar Andrey Ryabinin Committed by Linus Torvalds

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.comSigned-off-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5832fcf9
......@@ -11,7 +11,6 @@ config PARISC
select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_STRICT_KERNEL_RWX
select ARCH_HAS_UBSAN_SANITIZE_ALL
select ARCH_WANTS_UBSAN_NO_NULL
select ARCH_SUPPORTS_MEMORY_FAILURE
select RTC_CLASS
select RTC_DRV_GENERIC
......
......@@ -106,7 +106,6 @@ config S390
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF
select ARCH_WANTS_DYNAMIC_TASK_STRUCT
select ARCH_WANTS_UBSAN_NO_NULL
select ARCH_WANT_IPC_PARSE_VERSION
select BUILDTIME_EXTABLE_SORT
select CLONE_BACKWARDS2
......
config ARCH_HAS_UBSAN_SANITIZE_ALL
bool
config ARCH_WANTS_UBSAN_NO_NULL
def_bool n
config UBSAN
bool "Undefined behaviour sanity checker"
help
......@@ -39,14 +36,6 @@ config UBSAN_ALIGNMENT
Enabling this option on architectures that support unaligned
accesses may produce a lot of false positives.
config UBSAN_NULL
bool "Enable checking of null pointers"
depends on UBSAN
default y if !ARCH_WANTS_UBSAN_NO_NULL
help
This option enables detection of memory accesses via a
null pointer.
config TEST_UBSAN
tristate "Module for testing for undefined behavior detection"
depends on m && UBSAN
......
......@@ -14,10 +14,6 @@ ifdef CONFIG_UBSAN_ALIGNMENT
CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
endif
ifdef CONFIG_UBSAN_NULL
CFLAGS_UBSAN += $(call cc-option, -fsanitize=null)
endif
# -fsanitize=* options makes GCC less smart than usual and
# increase number of 'maybe-uninitialized false-positives
CFLAGS_UBSAN += $(call cc-option, -Wno-maybe-uninitialized)
......
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