The patch titled
Subject: lib/ubsan: remove null-pointer checks
has been added to the -mm tree. Its filename is
lib-ubsan-remove-null-pointer-checks.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-ubsan-remove-null-pointer-checks.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-ubsan-remove-null-pointer-checks.patch
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------------------------------------------------------
From: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxx
Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/parisc/Kconfig | 1 -
arch/s390/Kconfig | 1 -
lib/Kconfig.ubsan | 11 -----------
scripts/Makefile.ubsan | 4 ----
4 files changed, 17 deletions(-)
--- a/arch/parisc/Kconfig~lib-ubsan-remove-null-pointer-checks
+++ a/arch/parisc/Kconfig
@@ -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
--- a/arch/s390/Kconfig~lib-ubsan-remove-null-pointer-checks
+++ a/arch/s390/Kconfig
@@ -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
--- a/lib/Kconfig.ubsan~lib-ubsan-remove-null-pointer-checks
+++ a/lib/Kconfig.ubsan
@@ -1,9 +1,6 @@
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
--- a/scripts/Makefile.ubsan~lib-ubsan-remove-null-pointer-checks
+++ a/scripts/Makefile.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)
_
Patches currently in -mm which might be from aryabinin@xxxxxxxxxxxxx are
lib-ubsan-remove-null-pointer-checks.patch
mm-fadvise-fix-signed-overflow-ubsan-complaint.patch
kernel-memremap-kasan-make-zone_device-with-work-with-kasan.patch
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