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fix: resolve UB in _add, __sub, _mul for u8, u16, u32 #6654

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fix: resolve UB in _add, __sub, _mul for u8, u16, u32 #6654

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0b31117
fix: handle u32 & u16 subtract underflow manually
K1-R1 Oct 17, 2024
3f6244f
Merge branch 'master' into k1-r1-f4
K1-R1 Oct 17, 2024
699e96c
Merge branch 'master' into k1-r1-f4
K1-R1 Oct 21, 2024
f02f717
Merge branch 'master' into k1-r1-f4
K1-R1 Oct 23, 2024
260547e
fix: u32 add impl avoid UB
K1-R1 Oct 23, 2024
e83b2be
fix: u16 add impl avoid UB
K1-R1 Oct 23, 2024
b9959b1
fix: u32 add param names
K1-R1 Oct 23, 2024
75eba81
fix: u16 add param names
K1-R1 Oct 23, 2024
a735c12
fix: u32 sub impl avoid UB
K1-R1 Oct 23, 2024
8f71ac4
fix: u16 sub impl avoid UB
K1-R1 Oct 23, 2024
b1472c2
fix: u8 sub impl avoid UB
K1-R1 Oct 23, 2024
204bf27
fix: u32 mul impl avoid UB
K1-R1 Oct 23, 2024
18a71d3
fix: u16 mul impl avoid UB
K1-R1 Oct 23, 2024
ab7ac1e
chore: math_u8_underflow_sub test
K1-R1 Oct 23, 2024
2ca9571
chore: forc fmt
K1-R1 Oct 23, 2024
44915ca
Merge branch 'master' into k1-r1-f4
K1-R1 Oct 23, 2024
8cd71f3
Merge branch 'master' into k1-r1-f4
K1-R1 Oct 28, 2024
5d78172
Merge branch 'master' into k1-r1-f4
K1-R1 Oct 29, 2024
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181 changes: 152 additions & 29 deletions sway-lib-core/src/ops.sw
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Original file line number Diff line number Diff line change
Expand Up @@ -56,38 +56,62 @@ impl Add for u64 {
// Emulate overflowing arithmetic for non-64-bit integer types
impl Add for u32 {
fn add(self, other: Self) -> Self {
// any non-64-bit value is compiled to a u64 value under-the-hood
// constants (like Self::max() below) are also automatically promoted to u64
let res = __add(self, other);
// integer overflow
if __gt(res, Self::max()) {
let self_u64 = asm(input: self) {
input: u64
};
let other_u64 = asm(input: other) {
input: u64
};
let res_u64 = __add(self_u64, other_u64);
let max_u32_u64 = asm(input: Self::max()) {
input: u64
};
if __gt(res_u64, max_u32_u64) {
if panic_on_overflow_is_enabled() {
__revert(0)
} else {
// overflow enabled
// res % (Self::max() + 1)
__mod(res, __add(Self::max(), 1))
let res_u64 = __mod(res_u64, __add(max_u32_u64, 1));
asm(input: res_u64) {
input: u32
}
}
} else {
// no overflow
res
asm(input: res_u64) {
input: u32
}
}
}
}

impl Add for u16 {
fn add(self, other: Self) -> Self {
let res = __add(self, other);
if __gt(res, Self::max()) {
let self_u64 = asm(input: self) {
input: u64
};
let other_u64 = asm(input: other) {
input: u64
};
let res_u64 = __add(self_u64, other_u64);
let max_u16_u64 = asm(input: Self::max()) {
input: u64
};
if __gt(res_u64, max_u16_u64) {
if panic_on_overflow_is_enabled() {
__revert(0)
} else {
// overflow enabled
// res % (Self::max() + 1)
__mod(res, __add(Self::max(), 1))
let res_u64 = __mod(res_u64, __add(max_u16_u64, 1));
asm(input: res_u64) {
input: u16
}
}
} else {
res
asm(input: res_u64) {
input: u16
}
}
}
}
Expand Down Expand Up @@ -173,23 +197,96 @@ impl Subtract for u64 {
}
}

// unlike addition, underflowing subtraction does not need special treatment
// because VM handles underflow
impl Subtract for u32 {
fn subtract(self, other: Self) -> Self {
__sub(self, other)
let self_u64 = asm(input: self) {
input: u64
};
let other_u64 = asm(input: other) {
input: u64
};
let res_u64 = __sub(self_u64, other_u64);
let max_u32_u64 = asm(input: Self::max()) {
input: u64
};
if __gt(res_u64, max_u32_u64) {
if panic_on_overflow_is_enabled() {
__revert(0)
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} else {
// overflow enabled
// res % (Self::max() + 1)
let res_u64 = __mod(res_u64, __add(max_u32_u64, 1));
asm(input: res_u64) {
input: u32
}
}
} else {
asm(input: res_u64) {
input: u32
}
}
}
}

impl Subtract for u16 {
fn subtract(self, other: Self) -> Self {
__sub(self, other)
let self_u64 = asm(input: self) {
input: u64
};
let other_u64 = asm(input: other) {
input: u64
};
let res_u64 = __sub(self_u64, other_u64);
let max_u16_u64 = asm(input: Self::max()) {
input: u64
};
if __gt(res_u64, max_u16_u64) {
if panic_on_overflow_is_enabled() {
__revert(0)
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} else {
// overflow enabled
// res % (Self::max() + 1)
let res_u64 = __mod(res_u64, __add(max_u16_u64, 1));
asm(input: res_u64) {
input: u16
}
}
} else {
asm(input: res_u64) {
input: u16
}
}
}
}

impl Subtract for u8 {
fn subtract(self, other: Self) -> Self {
__sub(self, other)
let self_u64 = asm(input: self) {
input: u64
};
let other_u64 = asm(input: other) {
input: u64
};
let res_u64 = __sub(self_u64, other_u64);
let max_u8_u64 = asm(input: Self::max()) {
input: u64
};
if __gt(res_u64, max_u8_u64) {
if panic_on_overflow_is_enabled() {
__revert(0)
} else {
// overflow enabled
// res % (Self::max() + 1)
let res_u64 = __mod(res_u64, __add(max_u8_u64, 1));
asm(input: res_u64) {
input: u8
}
}
} else {
asm(input: res_u64) {
input: u8
}
}
}
}

Expand Down Expand Up @@ -246,36 +343,62 @@ impl Multiply for u64 {
// Emulate overflowing arithmetic for non-64-bit integer types
impl Multiply for u32 {
fn multiply(self, other: Self) -> Self {
// any non-64-bit value is compiled to a u64 value under-the-hood
// constants (like Self::max() below) are also automatically promoted to u64
let res = __mul(self, other);
if __gt(res, Self::max()) {
let self_u64 = asm(input: self) {
input: u64
};
let other_u64 = asm(input: other) {
input: u64
};
let res_u64 = __mul(self_u64, other_u64);
let max_u32_u64 = asm(input: Self::max()) {
input: u64
};
if __gt(res_u64, max_u32_u64) {
if panic_on_overflow_is_enabled() {
// integer overflow
__revert(0)
} else {
// overflow enabled
// res % (Self::max() + 1)
__mod(res, __add(Self::max(), 1))
let res_u64 = __mod(res_u64, __add(max_u32_u64, 1));
asm(input: res_u64) {
input: u32
}
}
} else {
// no overflow
res
asm(input: res_u64) {
input: u32
}
}
}
}

impl Multiply for u16 {
fn multiply(self, other: Self) -> Self {
let res = __mul(self, other);
if __gt(res, Self::max()) {
let self_u64 = asm(input: self) {
input: u64
};
let other_u64 = asm(input: other) {
input: u64
};
let res_u64 = __mul(self_u64, other_u64);
let max_u16_u64 = asm(input: Self::max()) {
input: u64
};
if __gt(res_u64, max_u16_u64) {
if panic_on_overflow_is_enabled() {
__revert(0)
} else {
__mod(res, __add(Self::max(), 1))
// overflow enabled
// res % (Self::max() + 1)
let res_u64 = __mod(res_u64, __add(max_u16_u64, 1));
asm(input: res_u64) {
input: u16
}
}
} else {
res
asm(input: res_u64) {
input: u16
}
}
}
}
Expand Down
76 changes: 76 additions & 0 deletions test/src/in_language_tests/test_programs/math_inline_tests/src/main.sw
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Original file line number Diff line number Diff line change
Expand Up @@ -900,6 +900,22 @@ fn math_u256_overflow_mul_revert() {
log(b);
}

#[test(should_revert)]
fn math_u16_underflow_sub_revert() {
let a = 0u16;
let b = 1u16;
let c = a - b;
log(c);
}

#[test(should_revert)]
fn math_u32_underflow_sub_revert() {
let a = 0u32;
let b = 1u32;
let c = a - b;
log(c);
}

#[test]
fn math_u8_overflow_add() {
let _ = disable_panic_on_overflow();
Expand All @@ -922,6 +938,26 @@ fn math_u8_overflow_add() {
require(e == u8::max() - 2, e);
}

#[test]
fn math_u8_underflow_sub() {
assert((u8::max() - u8::max()) == 0u8);
assert((u8::min() - u8::min()) == 0u8);
assert((10u8 - 5u8) == 5u8);

let _ = disable_panic_on_overflow();

let a = 0u8;
let b = 1u8;

let c = a - b;
assert(c == u8::max());

let d = u8::max();

let e = a - d;
assert(e == b);
}

#[test]
fn math_u16_overflow_add() {
let _ = disable_panic_on_overflow();
Expand All @@ -944,6 +980,26 @@ fn math_u16_overflow_add() {
require(e == u16::max() - 2, e);
}

#[test]
fn math_u16_underflow_sub() {
assert((u16::max() - u16::max()) == 0u16);
assert((u16::min() - u16::min()) == 0u16);
assert((10u16 - 5u16) == 5u16);

let _ = disable_panic_on_overflow();

let a = 0u16;
let b = 1u16;

let c = a - b;
assert(c == u16::max());

let d = u16::max();

let e = a - d;
assert(e == b);
}

#[test]
fn math_u32_overflow_add() {
let _ = disable_panic_on_overflow();
Expand All @@ -966,6 +1022,26 @@ fn math_u32_overflow_add() {
require(e == u32::max() - 2, e);
}

#[test]
fn math_u32_underflow_sub() {
assert((u32::max() - u32::max()) == 0u32);
assert((u32::min() - u32::min()) == 0u32);
assert((10u32 - 5u32) == 5u32);

let _ = disable_panic_on_overflow();

let a = 0u32;
let b = 1u32;

let c = a - b;
assert(c == u32::max());

let d = u32::max();

let e = a - d;
assert(e == b);
}

#[test]
fn math_u64_overflow_add() {
let _ = disable_panic_on_overflow();
Expand Down
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