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>

1 files changed, 0 insertions, 49 deletions

diff --git a/lib/test_ubsan.c b/lib/test_ubsan.c
index 5e5d9355ef49..7e7bbd0f3fd2 100644
--- a/lib/test_ubsan.c
+++ b/lib/test_ubsan.c
@@ -11,51 +11,6 @@ typedef void(*test_ubsan_fp)(void);
 			#config, IS_ENABLED(config) ? "y" : "n");	\
 	} while (0)
 
-static void test_ubsan_add_overflow(void)
-{
-	volatile int val = INT_MAX;
-	volatile unsigned int uval = UINT_MAX;
-
-	UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW);
-	val += 2;
-
-	UBSAN_TEST(CONFIG_UBSAN_UNSIGNED_OVERFLOW);
-	uval += 2;
-}
-
-static void test_ubsan_sub_overflow(void)
-{
-	volatile int val = INT_MIN;
-	volatile unsigned int uval = 0;
-	volatile int val2 = 2;
-
-	UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW);
-	val -= val2;
-
-	UBSAN_TEST(CONFIG_UBSAN_UNSIGNED_OVERFLOW);
-	uval -= val2;
-}
-
-static void test_ubsan_mul_overflow(void)
-{
-	volatile int val = INT_MAX / 2;
-	volatile unsigned int uval = UINT_MAX / 2;
-
-	UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW);
-	val *= 3;
-
-	UBSAN_TEST(CONFIG_UBSAN_UNSIGNED_OVERFLOW);
-	uval *= 3;
-}
-
-static void test_ubsan_negate_overflow(void)
-{
-	volatile int val = INT_MIN;
-
-	UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW);
-	val = -val;
-}
-
 static void test_ubsan_divrem_overflow(void)
 {
 	volatile int val = 16;
@@ -155,10 +110,6 @@ static void test_ubsan_object_size_mismatch(void)
 }
 
 static const test_ubsan_fp test_ubsan_array[] = {
-	test_ubsan_add_overflow,
-	test_ubsan_sub_overflow,
-	test_ubsan_mul_overflow,
-	test_ubsan_negate_overflow,
 	test_ubsan_shift_out_of_bounds,
 	test_ubsan_out_of_bounds,
 	test_ubsan_load_invalid_value,