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

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: 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

arch/parisc/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -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

arch/s390/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -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

lib/Kconfig.ubsan

+0 −11
Original line number Diff line number Diff line 
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

scripts/Makefile.ubsan

+0 −4
Original line number Diff line number Diff line
@@ -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)