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ubsan: remove overflow checks

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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 cdf8a76fda ("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>
This commit is contained in:
Andrey Ryabinin 2021-02-25 17:22:42 -08:00 committed by Linus Torvalds
parent d54ce6158e
commit 6aaa31aeb9
4 changed files with 0 additions and 136 deletions
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17
lib/Kconfig.ubsan
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@ -112,23 +112,6 @@ config UBSAN_UNREACHABLE
This option enables -fsanitize=unreachable which checks for control
flow reaching an expected-to-be-unreachable position.
config UBSAN_SIGNED_OVERFLOW
bool "Perform checking for signed arithmetic overflow"
default UBSAN
depends on $(cc-option,-fsanitize=signed-integer-overflow)
help
This option enables -fsanitize=signed-integer-overflow which checks
for overflow of any arithmetic operations with signed integers.
config UBSAN_UNSIGNED_OVERFLOW
bool "Perform checking for unsigned arithmetic overflow"
depends on $(cc-option,-fsanitize=unsigned-integer-overflow)
depends on !X86_32 # avoid excessive stack usage on x86-32/clang
help
This option enables -fsanitize=unsigned-integer-overflow which checks
for overflow of any arithmetic operations with unsigned integers. This
currently causes x86 to fail to boot.
config UBSAN_OBJECT_SIZE
bool "Perform checking for accesses beyond the end of objects"
default UBSAN

49
lib/test_ubsan.c
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@ -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,

68
lib/ubsan.c
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@ -163,74 +163,6 @@ static void ubsan_epilogue(void)
}
}
static void handle_overflow(struct overflow_data *data, void *lhs,
void *rhs, char op)
{
struct type_descriptor *type = data->type;
char lhs_val_str[VALUE_LENGTH];
char rhs_val_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, type_is_signed(type) ?
"signed-integer-overflow" :
"unsigned-integer-overflow");
val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
pr_err("%s %c %s cannot be represented in type %s\n",
lhs_val_str,
op,
rhs_val_str,
type->type_name);
ubsan_epilogue();
}
void __ubsan_handle_add_overflow(void *data,
void *lhs, void *rhs)
{
handle_overflow(data, lhs, rhs, '+');
}
EXPORT_SYMBOL(__ubsan_handle_add_overflow);
void __ubsan_handle_sub_overflow(void *data,
void *lhs, void *rhs)
{
handle_overflow(data, lhs, rhs, '-');
}
EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
void __ubsan_handle_mul_overflow(void *data,
void *lhs, void *rhs)
{
handle_overflow(data, lhs, rhs, '*');
}
EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
void __ubsan_handle_negate_overflow(void *_data, void *old_val)
{
struct overflow_data *data = _data;
char old_val_str[VALUE_LENGTH];
if (suppress_report(&data->location))
return;
ubsan_prologue(&data->location, "negation-overflow");
val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
pr_err("negation of %s cannot be represented in type %s:\n",
old_val_str, data->type->type_name);
ubsan_epilogue();
}
EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs)
{
struct overflow_data *data = _data;

2
scripts/Makefile.ubsan
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@ -8,8 +8,6 @@ ubsan-cflags-$(CONFIG_UBSAN_LOCAL_BOUNDS) += -fsanitize=local-bounds
ubsan-cflags-$(CONFIG_UBSAN_SHIFT) += -fsanitize=shift
ubsan-cflags-$(CONFIG_UBSAN_DIV_ZERO) += -fsanitize=integer-divide-by-zero
ubsan-cflags-$(CONFIG_UBSAN_UNREACHABLE) += -fsanitize=unreachable
ubsan-cflags-$(CONFIG_UBSAN_SIGNED_OVERFLOW) += -fsanitize=signed-integer-overflow
ubsan-cflags-$(CONFIG_UBSAN_UNSIGNED_OVERFLOW) += -fsanitize=unsigned-integer-overflow
ubsan-cflags-$(CONFIG_UBSAN_OBJECT_SIZE) += -fsanitize=object-size
ubsan-cflags-$(CONFIG_UBSAN_BOOL) += -fsanitize=bool
ubsan-cflags-$(CONFIG_UBSAN_ENUM) += -fsanitize=enum