[PATCH 11/82] arm64: atomics: lse: Silence intentional wrapping addition

[PATCH 11/82] arm64: atomics: lse: Silence intentional wrapping addition

[Kees Cook]

Annotate atomic_add_return() and atomic_sub_return() to avoid signed
overflow instrumentation. They are expected to wrap around.

Cc: Will Deacon <will@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/include/asm/atomic_lse.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h
index 87f568a94e55..30572458d702 100644
--- a/arch/arm64/include/asm/atomic_lse.h
+++ b/arch/arm64/include/asm/atomic_lse.h
@@ -79,13 +79,13 @@ ATOMIC_FETCH_OP_SUB(        )
 #undef ATOMIC_FETCH_OP_SUB
 
 #define ATOMIC_OP_ADD_SUB_RETURN(name)					\
-static __always_inline int						\
+static __always_inline __signed_wrap int				\
 __lse_atomic_add_return##name(int i, atomic_t *v)			\
 {									\
 	return __lse_atomic_fetch_add##name(i, v) + i;			\
 }									\
 									\
-static __always_inline int						\
+static __always_inline __signed_wrap int				\
 __lse_atomic_sub_return##name(int i, atomic_t *v)			\
 {									\
 	return __lse_atomic_fetch_sub(i, v) - i;			\
@@ -186,13 +186,13 @@ ATOMIC64_FETCH_OP_SUB(        )
 #undef ATOMIC64_FETCH_OP_SUB
 
 #define ATOMIC64_OP_ADD_SUB_RETURN(name)				\
-static __always_inline long						\
+static __always_inline __signed_wrap long				\
 __lse_atomic64_add_return##name(s64 i, atomic64_t *v)			\
 {									\
 	return __lse_atomic64_fetch_add##name(i, v) + i;		\
 }									\
 									\
-static __always_inline long						\
+static __always_inline __signed_wrap long				\
 __lse_atomic64_sub_return##name(s64 i, atomic64_t *v)			\
 {									\
 	return __lse_atomic64_fetch_sub##name(i, v) - i;		\
-- 
2.34.1


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Re: [PATCH 11/82] arm64: atomics: lse: Silence intentional wrapping addition

[Mark Rutland]

On Mon, Jan 22, 2024 at 04:26:46PM -0800, Kees Cook wrote:
> Annotate atomic_add_return() and atomic_sub_return() to avoid signed
> overflow instrumentation. They are expected to wrap around.
> 
> Cc: Will Deacon <will@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/arm64/include/asm/atomic_lse.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h
> index 87f568a94e55..30572458d702 100644
> --- a/arch/arm64/include/asm/atomic_lse.h
> +++ b/arch/arm64/include/asm/atomic_lse.h
> @@ -79,13 +79,13 @@ ATOMIC_FETCH_OP_SUB(        )
>  #undef ATOMIC_FETCH_OP_SUB
>  
>  #define ATOMIC_OP_ADD_SUB_RETURN(name)					\
> -static __always_inline int						\
> +static __always_inline __signed_wrap int				\
>  __lse_atomic_add_return##name(int i, atomic_t *v)			\
>  {									\
>  	return __lse_atomic_fetch_add##name(i, v) + i;			\
>  }									\

I'd strongly prefer using add_wrap() rather than annotating the function, i.e.
make this:

  static __always_inline int						\
  __lse_atomic_add_return##name(int i, atomic_t *v)			\
  {									\
  	return add_wrap(__lse_atomic_fetch_add##name(i, v), i);		\
  }									\

Likewise for the other instances below.

With that, this looks fine to me.

Mark.

>  									\
> -static __always_inline int						\
> +static __always_inline __signed_wrap int				\
>  __lse_atomic_sub_return##name(int i, atomic_t *v)			\
>  {									\
>  	return __lse_atomic_fetch_sub(i, v) - i;			\
> @@ -186,13 +186,13 @@ ATOMIC64_FETCH_OP_SUB(        )
>  #undef ATOMIC64_FETCH_OP_SUB
>  
>  #define ATOMIC64_OP_ADD_SUB_RETURN(name)				\
> -static __always_inline long						\
> +static __always_inline __signed_wrap long				\
>  __lse_atomic64_add_return##name(s64 i, atomic64_t *v)			\
>  {									\
>  	return __lse_atomic64_fetch_add##name(i, v) + i;		\
>  }									\
>  									\
> -static __always_inline long						\
> +static __always_inline __signed_wrap long				\
>  __lse_atomic64_sub_return##name(s64 i, atomic64_t *v)			\
>  {									\
>  	return __lse_atomic64_fetch_sub##name(i, v) - i;		\
> -- 
> 2.34.1
> 

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[PATCH 24/82] KVM: arm64: vgic: Refactor intentional wrap-around calculation

[Kees Cook]

In an effort to separate intentional arithmetic wrap-around from
unexpected wrap-around, we need to refactor places that depend on this
kind of math. One of the most common code patterns of this is:

	VAR + value < VAR

Notably, this is considered "undefined behavior" for signed and pointer
types, which the kernel works around by using the -fno-strict-overflow
option in the build[1] (which used to just be -fwrapv). Regardless, we
want to get the kernel source to the position where we can meaningfully
instrument arithmetic wrap-around conditions and catch them when they
are unexpected, regardless of whether they are signed[2], unsigned[3],
or pointer[4] types.

Refactor open-coded unsigned wrap-around addition test to use
check_add_overflow(), retaining the result for later usage (which removes
the redundant open-coded addition). This paves the way to enabling the
wrap-around sanitizers in the future.

Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
Link: https://github.com/KSPP/linux/issues/26 [2]
Link: https://github.com/KSPP/linux/issues/27 [3]
Link: https://github.com/KSPP/linux/issues/344 [4]
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Zenghui Yu <yuzenghui@huawei.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Reiji Watanabe <reijiw@google.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: Ricardo Koller <ricarkol@google.com>
Cc: Raghavendra Rao Ananta <rananta@google.com>
Cc: Quentin Perret <qperret@google.com>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: kvmarm@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/kvm/vgic/vgic-kvm-device.c |  6 ++++--
 arch/arm64/kvm/vgic/vgic-v2.c         | 10 ++++++----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
index f48b8dab8b3d..0eec5344d203 100644
--- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
+++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
@@ -18,17 +18,19 @@ int vgic_check_iorange(struct kvm *kvm, phys_addr_t ioaddr,
 		       phys_addr_t addr, phys_addr_t alignment,
 		       phys_addr_t size)
 {
+	phys_addr_t sum;
+
 	if (!IS_VGIC_ADDR_UNDEF(ioaddr))
 		return -EEXIST;
 
 	if (!IS_ALIGNED(addr, alignment) || !IS_ALIGNED(size, alignment))
 		return -EINVAL;
 
-	if (addr + size < addr)
+	if (check_add_overflow(addr, size, &sum))
 		return -EINVAL;
 
 	if (addr & ~kvm_phys_mask(&kvm->arch.mmu) ||
-	    (addr + size) > kvm_phys_size(&kvm->arch.mmu))
+	    sum > kvm_phys_size(&kvm->arch.mmu))
 		return -E2BIG;
 
 	return 0;
diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c
index 7e9cdb78f7ce..c8d1e965d3b7 100644
--- a/arch/arm64/kvm/vgic/vgic-v2.c
+++ b/arch/arm64/kvm/vgic/vgic-v2.c
@@ -273,14 +273,16 @@ void vgic_v2_enable(struct kvm_vcpu *vcpu)
 /* check for overlapping regions and for regions crossing the end of memory */
 static bool vgic_v2_check_base(gpa_t dist_base, gpa_t cpu_base)
 {
-	if (dist_base + KVM_VGIC_V2_DIST_SIZE < dist_base)
+	gpa_t dist_sum, cpu_sum;
+
+	if (check_add_overflow(dist_base, KVM_VGIC_V2_DIST_SIZE, &dist_sum))
 		return false;
-	if (cpu_base + KVM_VGIC_V2_CPU_SIZE < cpu_base)
+	if (check_add_overflow(cpu_base, KVM_VGIC_V2_CPU_SIZE, &cpu_sum))
 		return false;
 
-	if (dist_base + KVM_VGIC_V2_DIST_SIZE <= cpu_base)
+	if (dist_sum <= cpu_base)
 		return true;
-	if (cpu_base + KVM_VGIC_V2_CPU_SIZE <= dist_base)
+	if (cpu_sum <= dist_base)
 		return true;
 
 	return false;
-- 
2.34.1


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Re: [PATCH 24/82] KVM: arm64: vgic: Refactor intentional wrap-around calculation

[Marc Zyngier]

On Tue, 23 Jan 2024 00:26:59 +0000,
Kees Cook <keescook@chromium.org> wrote:
> 
> In an effort to separate intentional arithmetic wrap-around from
> unexpected wrap-around, we need to refactor places that depend on this
> kind of math. One of the most common code patterns of this is:
> 
> 	VAR + value < VAR
> 
> Notably, this is considered "undefined behavior" for signed and pointer
> types, which the kernel works around by using the -fno-strict-overflow
> option in the build[1] (which used to just be -fwrapv). Regardless, we
> want to get the kernel source to the position where we can meaningfully
> instrument arithmetic wrap-around conditions and catch them when they
> are unexpected, regardless of whether they are signed[2], unsigned[3],
> or pointer[4] types.
> 
> Refactor open-coded unsigned wrap-around addition test to use
> check_add_overflow(), retaining the result for later usage (which removes
> the redundant open-coded addition). This paves the way to enabling the
> wrap-around sanitizers in the future.
> 
> Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
> Link: https://github.com/KSPP/linux/issues/26 [2]
> Link: https://github.com/KSPP/linux/issues/27 [3]
> Link: https://github.com/KSPP/linux/issues/344 [4]
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Oliver Upton <oliver.upton@linux.dev>
> Cc: James Morse <james.morse@arm.com>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Zenghui Yu <yuzenghui@huawei.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Reiji Watanabe <reijiw@google.com>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: Ricardo Koller <ricarkol@google.com>
> Cc: Raghavendra Rao Ananta <rananta@google.com>
> Cc: Quentin Perret <qperret@google.com>
> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: kvmarm@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/arm64/kvm/vgic/vgic-kvm-device.c |  6 ++++--
>  arch/arm64/kvm/vgic/vgic-v2.c         | 10 ++++++----
>  2 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
> index f48b8dab8b3d..0eec5344d203 100644
> --- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
> +++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
> @@ -18,17 +18,19 @@ int vgic_check_iorange(struct kvm *kvm, phys_addr_t ioaddr,
>  		       phys_addr_t addr, phys_addr_t alignment,
>  		       phys_addr_t size)
>  {
> +	phys_addr_t sum;
> +
>  	if (!IS_VGIC_ADDR_UNDEF(ioaddr))
>  		return -EEXIST;
>  
>  	if (!IS_ALIGNED(addr, alignment) || !IS_ALIGNED(size, alignment))
>  		return -EINVAL;
>  
> -	if (addr + size < addr)
> +	if (check_add_overflow(addr, size, &sum))
>  		return -EINVAL;
>  
>  	if (addr & ~kvm_phys_mask(&kvm->arch.mmu) ||
> -	    (addr + size) > kvm_phys_size(&kvm->arch.mmu))
> +	    sum > kvm_phys_size(&kvm->arch.mmu))

nit: 'sum' doesn't mean much in this context. Something like 'end'
would be much more descriptive.

>  		return -E2BIG;
>  
>  	return 0;
> diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c
> index 7e9cdb78f7ce..c8d1e965d3b7 100644
> --- a/arch/arm64/kvm/vgic/vgic-v2.c
> +++ b/arch/arm64/kvm/vgic/vgic-v2.c
> @@ -273,14 +273,16 @@ void vgic_v2_enable(struct kvm_vcpu *vcpu)
>  /* check for overlapping regions and for regions crossing the end of memory */
>  static bool vgic_v2_check_base(gpa_t dist_base, gpa_t cpu_base)
>  {
> -	if (dist_base + KVM_VGIC_V2_DIST_SIZE < dist_base)
> +	gpa_t dist_sum, cpu_sum;

Same here: dist_end, cpu_end.

> +
> +	if (check_add_overflow(dist_base, KVM_VGIC_V2_DIST_SIZE, &dist_sum))
>  		return false;
> -	if (cpu_base + KVM_VGIC_V2_CPU_SIZE < cpu_base)
> +	if (check_add_overflow(cpu_base, KVM_VGIC_V2_CPU_SIZE, &cpu_sum))
>  		return false;
>  
> -	if (dist_base + KVM_VGIC_V2_DIST_SIZE <= cpu_base)
> +	if (dist_sum <= cpu_base)
>  		return true;
> -	if (cpu_base + KVM_VGIC_V2_CPU_SIZE <= dist_base)
> +	if (cpu_sum <= dist_base)
>  		return true;
>  
>  	return false;

With these nits addressed, and assuming you intend to merge the whole
series yourself:

Acked-by: Marc Zyngier <maz@kernel.org>

	M.

-- 
Without deviation from the norm, progress is not possible.

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Re: [PATCH 24/82] KVM: arm64: vgic: Refactor intentional wrap-around calculation

[Eric Auger]

On 1/23/24 11:49, Marc Zyngier wrote:
> On Tue, 23 Jan 2024 00:26:59 +0000,
> Kees Cook <keescook@chromium.org> wrote:
>> In an effort to separate intentional arithmetic wrap-around from
>> unexpected wrap-around, we need to refactor places that depend on this
>> kind of math. One of the most common code patterns of this is:
>>
>> 	VAR + value < VAR
>>
>> Notably, this is considered "undefined behavior" for signed and pointer
>> types, which the kernel works around by using the -fno-strict-overflow
>> option in the build[1] (which used to just be -fwrapv). Regardless, we
>> want to get the kernel source to the position where we can meaningfully
>> instrument arithmetic wrap-around conditions and catch them when they
>> are unexpected, regardless of whether they are signed[2], unsigned[3],
>> or pointer[4] types.
>>
>> Refactor open-coded unsigned wrap-around addition test to use
>> check_add_overflow(), retaining the result for later usage (which removes
>> the redundant open-coded addition). This paves the way to enabling the
>> wrap-around sanitizers in the future.
>>
>> Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
>> Link: https://github.com/KSPP/linux/issues/26 [2]
>> Link: https://github.com/KSPP/linux/issues/27 [3]
>> Link: https://github.com/KSPP/linux/issues/344 [4]
>> Cc: Marc Zyngier <maz@kernel.org>
>> Cc: Oliver Upton <oliver.upton@linux.dev>
>> Cc: James Morse <james.morse@arm.com>
>> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
>> Cc: Zenghui Yu <yuzenghui@huawei.com>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Reiji Watanabe <reijiw@google.com>
>> Cc: Eric Auger <eric.auger@redhat.com>
>> Cc: Ricardo Koller <ricarkol@google.com>
>> Cc: Raghavendra Rao Ananta <rananta@google.com>
>> Cc: Quentin Perret <qperret@google.com>
>> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
>> Cc: linux-arm-kernel@lists.infradead.org
>> Cc: kvmarm@lists.linux.dev
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> ---
>>  arch/arm64/kvm/vgic/vgic-kvm-device.c |  6 ++++--
>>  arch/arm64/kvm/vgic/vgic-v2.c         | 10 ++++++----
>>  2 files changed, 10 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
>> index f48b8dab8b3d..0eec5344d203 100644
>> --- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
>> +++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
>> @@ -18,17 +18,19 @@ int vgic_check_iorange(struct kvm *kvm, phys_addr_t ioaddr,
>>  		       phys_addr_t addr, phys_addr_t alignment,
>>  		       phys_addr_t size)
>>  {
>> +	phys_addr_t sum;
>> +
>>  	if (!IS_VGIC_ADDR_UNDEF(ioaddr))
>>  		return -EEXIST;
>>  
>>  	if (!IS_ALIGNED(addr, alignment) || !IS_ALIGNED(size, alignment))
>>  		return -EINVAL;
>>  
>> -	if (addr + size < addr)
>> +	if (check_add_overflow(addr, size, &sum))
>>  		return -EINVAL;
>>  
>>  	if (addr & ~kvm_phys_mask(&kvm->arch.mmu) ||
>> -	    (addr + size) > kvm_phys_size(&kvm->arch.mmu))
>> +	    sum > kvm_phys_size(&kvm->arch.mmu))
> nit: 'sum' doesn't mean much in this context. Something like 'end'
> would be much more descriptive.
>
>>  		return -E2BIG;
>>  
>>  	return 0;
>> diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c
>> index 7e9cdb78f7ce..c8d1e965d3b7 100644
>> --- a/arch/arm64/kvm/vgic/vgic-v2.c
>> +++ b/arch/arm64/kvm/vgic/vgic-v2.c
>> @@ -273,14 +273,16 @@ void vgic_v2_enable(struct kvm_vcpu *vcpu)
>>  /* check for overlapping regions and for regions crossing the end of memory */
>>  static bool vgic_v2_check_base(gpa_t dist_base, gpa_t cpu_base)
>>  {
>> -	if (dist_base + KVM_VGIC_V2_DIST_SIZE < dist_base)
>> +	gpa_t dist_sum, cpu_sum;
> Same here: dist_end, cpu_end.
I do agree.
>
>> +
>> +	if (check_add_overflow(dist_base, KVM_VGIC_V2_DIST_SIZE, &dist_sum))
>>  		return false;
>> -	if (cpu_base + KVM_VGIC_V2_CPU_SIZE < cpu_base)
>> +	if (check_add_overflow(cpu_base, KVM_VGIC_V2_CPU_SIZE, &cpu_sum))
>>  		return false;
>>  
>> -	if (dist_base + KVM_VGIC_V2_DIST_SIZE <= cpu_base)
>> +	if (dist_sum <= cpu_base)
>>  		return true;
>> -	if (cpu_base + KVM_VGIC_V2_CPU_SIZE <= dist_base)
>> +	if (cpu_sum <= dist_base)
>>  		return true;
>>  
>>  	return false;
> With these nits addressed, and assuming you intend to merge the whole
> series yourself:
>
> Acked-by: Marc Zyngier <maz@kernel.org>
assuming above suggested changes,

Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
>
> 	M.
>


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[PATCH 38/82] arm: 3117/1: Refactor intentional wrap-around test

[Kees Cook]

In an effort to separate intentional arithmetic wrap-around from
unexpected wrap-around, we need to refactor places that depend on this
kind of math. One of the most common code patterns of this is:

	VAR + value < VAR

Notably, this is considered "undefined behavior" for signed and pointer
types, which the kernel works around by using the -fno-strict-overflow
option in the build[1] (which used to just be -fwrapv). Regardless, we
want to get the kernel source to the position where we can meaningfully
instrument arithmetic wrap-around conditions and catch them when they
are unexpected, regardless of whether they are signed[2], unsigned[3],
or pointer[4] types.

Refactor open-coded wrap-around addition test to use add_would_overflow().
This paves the way to enabling the wrap-around sanitizers in the future.

Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
Link: https://github.com/KSPP/linux/issues/26 [2]
Link: https://github.com/KSPP/linux/issues/27 [3]
Link: https://github.com/KSPP/linux/issues/344 [4]
Cc: Russell King <linux@armlinux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm/nwfpe/softfloat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/nwfpe/softfloat.c b/arch/arm/nwfpe/softfloat.c
index ffa6b438786b..0635b1eda1d3 100644
--- a/arch/arm/nwfpe/softfloat.c
+++ b/arch/arm/nwfpe/softfloat.c
@@ -603,7 +603,7 @@ static floatx80
     roundBits = zSig0 & roundMask;
     if ( 0x7FFD <= (bits32) ( zExp - 1 ) ) {
         if (    ( 0x7FFE < zExp )
-             || ( ( zExp == 0x7FFE ) && ( zSig0 + roundIncrement < zSig0 ) )
+             || ( ( zExp == 0x7FFE ) && (add_would_overflow(zSig0, roundIncrement)) )
            ) {
             goto overflow;
         }
-- 
2.34.1


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Re: [PATCH 38/82] arm: 3117/1: Refactor intentional wrap-around test

[Mark Rutland]

The commit title is odd here; '3117/1' is the patch tracker name for the last
patch. The title should probably be:

	arm: nwfpe: Refactor intentional wrap-around test

Mark.

On Mon, Jan 22, 2024 at 04:27:13PM -0800, Kees Cook wrote:
> In an effort to separate intentional arithmetic wrap-around from
> unexpected wrap-around, we need to refactor places that depend on this
> kind of math. One of the most common code patterns of this is:
> 
> 	VAR + value < VAR
> 
> Notably, this is considered "undefined behavior" for signed and pointer
> types, which the kernel works around by using the -fno-strict-overflow
> option in the build[1] (which used to just be -fwrapv). Regardless, we
> want to get the kernel source to the position where we can meaningfully
> instrument arithmetic wrap-around conditions and catch them when they
> are unexpected, regardless of whether they are signed[2], unsigned[3],
> or pointer[4] types.
> 
> Refactor open-coded wrap-around addition test to use add_would_overflow().
> This paves the way to enabling the wrap-around sanitizers in the future.
> 
> Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
> Link: https://github.com/KSPP/linux/issues/26 [2]
> Link: https://github.com/KSPP/linux/issues/27 [3]
> Link: https://github.com/KSPP/linux/issues/344 [4]
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/arm/nwfpe/softfloat.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/nwfpe/softfloat.c b/arch/arm/nwfpe/softfloat.c
> index ffa6b438786b..0635b1eda1d3 100644
> --- a/arch/arm/nwfpe/softfloat.c
> +++ b/arch/arm/nwfpe/softfloat.c
> @@ -603,7 +603,7 @@ static floatx80
>      roundBits = zSig0 & roundMask;
>      if ( 0x7FFD <= (bits32) ( zExp - 1 ) ) {
>          if (    ( 0x7FFE < zExp )
> -             || ( ( zExp == 0x7FFE ) && ( zSig0 + roundIncrement < zSig0 ) )
> +             || ( ( zExp == 0x7FFE ) && (add_would_overflow(zSig0, roundIncrement)) )
>             ) {
>              goto overflow;
>          }
> -- 
> 2.34.1
> 
> 

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Re: [PATCH 38/82] arm: 3117/1: Refactor intentional wrap-around test

[Kees Cook]

On Tue, Jan 23, 2024 at 09:56:22AM +0000, Mark Rutland wrote:
> The commit title is odd here; '3117/1' is the patch tracker name for the last
> patch. The title should probably be:
> 
> 	arm: nwfpe: Refactor intentional wrap-around test

Whoops, yes. I need to teach my prefix-guessing script to drop the ARM
patch tracker numbers...

-Kees

> 
> Mark.
> 
> On Mon, Jan 22, 2024 at 04:27:13PM -0800, Kees Cook wrote:
> > In an effort to separate intentional arithmetic wrap-around from
> > unexpected wrap-around, we need to refactor places that depend on this
> > kind of math. One of the most common code patterns of this is:
> > 
> > 	VAR + value < VAR
> > 
> > Notably, this is considered "undefined behavior" for signed and pointer
> > types, which the kernel works around by using the -fno-strict-overflow
> > option in the build[1] (which used to just be -fwrapv). Regardless, we
> > want to get the kernel source to the position where we can meaningfully
> > instrument arithmetic wrap-around conditions and catch them when they
> > are unexpected, regardless of whether they are signed[2], unsigned[3],
> > or pointer[4] types.
> > 
> > Refactor open-coded wrap-around addition test to use add_would_overflow().
> > This paves the way to enabling the wrap-around sanitizers in the future.
> > 
> > Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
> > Link: https://github.com/KSPP/linux/issues/26 [2]
> > Link: https://github.com/KSPP/linux/issues/27 [3]
> > Link: https://github.com/KSPP/linux/issues/344 [4]
> > Cc: Russell King <linux@armlinux.org.uk>
> > Cc: linux-arm-kernel@lists.infradead.org
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> >  arch/arm/nwfpe/softfloat.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm/nwfpe/softfloat.c b/arch/arm/nwfpe/softfloat.c
> > index ffa6b438786b..0635b1eda1d3 100644
> > --- a/arch/arm/nwfpe/softfloat.c
> > +++ b/arch/arm/nwfpe/softfloat.c
> > @@ -603,7 +603,7 @@ static floatx80
> >      roundBits = zSig0 & roundMask;
> >      if ( 0x7FFD <= (bits32) ( zExp - 1 ) ) {
> >          if (    ( 0x7FFE < zExp )
> > -             || ( ( zExp == 0x7FFE ) && ( zSig0 + roundIncrement < zSig0 ) )
> > +             || ( ( zExp == 0x7FFE ) && (add_would_overflow(zSig0, roundIncrement)) )
> >             ) {
> >              goto overflow;
> >          }
> > -- 
> > 2.34.1
> > 
> > 

-- 
Kees Cook

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[PATCH 40/82] arm64: stacktrace: Refactor intentional wrap-around test

[Kees Cook]

In an effort to separate intentional arithmetic wrap-around from
unexpected wrap-around, we need to refactor places that depend on this
kind of math. One of the most common code patterns of this is:

	VAR + value < VAR

Notably, this is considered "undefined behavior" for signed and pointer
types, which the kernel works around by using the -fno-strict-overflow
option in the build[1] (which used to just be -fwrapv). Regardless, we
want to get the kernel source to the position where we can meaningfully
instrument arithmetic wrap-around conditions and catch them when they
are unexpected, regardless of whether they are signed[2], unsigned[3],
or pointer[4] types.

Refactor open-coded wrap-around addition test to use add_would_overflow().
This paves the way to enabling the wrap-around sanitizers in the future.

Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
Link: https://github.com/KSPP/linux/issues/26 [2]
Link: https://github.com/KSPP/linux/issues/27 [3]
Link: https://github.com/KSPP/linux/issues/344 [4]
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/include/asm/stacktrace/common.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
index f63dc654e545..6e0cb84961f8 100644
--- a/arch/arm64/include/asm/stacktrace/common.h
+++ b/arch/arm64/include/asm/stacktrace/common.h
@@ -49,7 +49,7 @@ static inline bool stackinfo_on_stack(const struct stack_info *info,
 	if (!info->low)
 		return false;
 
-	if (sp < info->low || sp + size < sp || sp + size > info->high)
+	if (sp < info->low || add_would_overflow(sp, size) || sp + size > info->high)
 		return false;
 
 	return true;
-- 
2.34.1


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Re: [PATCH 40/82] arm64: stacktrace: Refactor intentional wrap-around test

[Mark Rutland]

On Mon, Jan 22, 2024 at 04:27:15PM -0800, Kees Cook wrote:
> In an effort to separate intentional arithmetic wrap-around from
> unexpected wrap-around, we need to refactor places that depend on this
> kind of math. One of the most common code patterns of this is:
> 
> 	VAR + value < VAR
> 
> Notably, this is considered "undefined behavior" for signed and pointer
> types, which the kernel works around by using the -fno-strict-overflow
> option in the build[1] (which used to just be -fwrapv). Regardless, we
> want to get the kernel source to the position where we can meaningfully
> instrument arithmetic wrap-around conditions and catch them when they
> are unexpected, regardless of whether they are signed[2], unsigned[3],
> or pointer[4] types.
> 
> Refactor open-coded wrap-around addition test to use add_would_overflow().
> This paves the way to enabling the wrap-around sanitizers in the future.
> 
> Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
> Link: https://github.com/KSPP/linux/issues/26 [2]
> Link: https://github.com/KSPP/linux/issues/27 [3]
> Link: https://github.com/KSPP/linux/issues/344 [4]
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Kalesh Singh <kaleshsingh@google.com>
> Cc: Fuad Tabba <tabba@google.com>
> Cc: Mark Brown <broonie@kernel.org>
> Cc: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/arm64/include/asm/stacktrace/common.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
> index f63dc654e545..6e0cb84961f8 100644
> --- a/arch/arm64/include/asm/stacktrace/common.h
> +++ b/arch/arm64/include/asm/stacktrace/common.h
> @@ -49,7 +49,7 @@ static inline bool stackinfo_on_stack(const struct stack_info *info,
>  	if (!info->low)
>  		return false;
>  
> -	if (sp < info->low || sp + size < sp || sp + size > info->high)
> +	if (sp < info->low || add_would_overflow(sp, size) || sp + size > info->high)
>  		return false;

This looks fine to me, so FWIW:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

>  
>  	return true;
> -- 
> 2.34.1
> 

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[PATCH 57/82] KVM: arm64: vgic-v3: Refactor intentional wrap-around test

[Kees Cook]

In an effort to separate intentional arithmetic wrap-around from
unexpected wrap-around, we need to refactor places that depend on this
kind of math. One of the most common code patterns of this is:

	VAR + value < VAR

Notably, this is considered "undefined behavior" for signed and pointer
types, which the kernel works around by using the -fno-strict-overflow
option in the build[1] (which used to just be -fwrapv). Regardless, we
want to get the kernel source to the position where we can meaningfully
instrument arithmetic wrap-around conditions and catch them when they
are unexpected, regardless of whether they are signed[2], unsigned[3],
or pointer[4] types.

Refactor open-coded wrap-around addition test to use add_would_overflow().
This paves the way to enabling the wrap-around sanitizers in the future.

Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
Link: https://github.com/KSPP/linux/issues/26 [2]
Link: https://github.com/KSPP/linux/issues/27 [3]
Link: https://github.com/KSPP/linux/issues/344 [4]
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Zenghui Yu <yuzenghui@huawei.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: kvmarm@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/kvm/vgic/vgic-mmio-v3.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
index c15ee1df036a..860b774c0c13 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
@@ -863,7 +863,7 @@ static int vgic_v3_alloc_redist_region(struct kvm *kvm, uint32_t index,
 	int ret;
 
 	/* cross the end of memory ? */
-	if (base + size < base)
+	if (add_would_overflow(base, size))
 		return -EINVAL;
 
 	if (list_empty(rd_regions)) {
-- 
2.34.1


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Re: [PATCH 57/82] KVM: arm64: vgic-v3: Refactor intentional wrap-around test

[Marc Zyngier]

On Tue, 23 Jan 2024 00:27:32 +0000,
Kees Cook <keescook@chromium.org> wrote:
> 
> In an effort to separate intentional arithmetic wrap-around from
> unexpected wrap-around, we need to refactor places that depend on this
> kind of math. One of the most common code patterns of this is:
> 
> 	VAR + value < VAR
> 
> Notably, this is considered "undefined behavior" for signed and pointer
> types, which the kernel works around by using the -fno-strict-overflow
> option in the build[1] (which used to just be -fwrapv). Regardless, we
> want to get the kernel source to the position where we can meaningfully
> instrument arithmetic wrap-around conditions and catch them when they
> are unexpected, regardless of whether they are signed[2], unsigned[3],
> or pointer[4] types.
> 
> Refactor open-coded wrap-around addition test to use add_would_overflow().
> This paves the way to enabling the wrap-around sanitizers in the future.
> 
> Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
> Link: https://github.com/KSPP/linux/issues/26 [2]
> Link: https://github.com/KSPP/linux/issues/27 [3]
> Link: https://github.com/KSPP/linux/issues/344 [4]
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Oliver Upton <oliver.upton@linux.dev>
> Cc: James Morse <james.morse@arm.com>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Zenghui Yu <yuzenghui@huawei.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: kvmarm@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/arm64/kvm/vgic/vgic-mmio-v3.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> index c15ee1df036a..860b774c0c13 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> @@ -863,7 +863,7 @@ static int vgic_v3_alloc_redist_region(struct kvm *kvm, uint32_t index,
>  	int ret;
>  
>  	/* cross the end of memory ? */
> -	if (base + size < base)
> +	if (add_would_overflow(base, size))
>  		return -EINVAL;
>  
>  	if (list_empty(rd_regions)) {

Acked-by: Marc Zyngier <maz@kernel.org>

	M.

-- 
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Re: [PATCH 57/82] KVM: arm64: vgic-v3: Refactor intentional wrap-around test

[Eric Auger]

On 1/23/24 01:27, Kees Cook wrote:
> In an effort to separate intentional arithmetic wrap-around from
> unexpected wrap-around, we need to refactor places that depend on this
> kind of math. One of the most common code patterns of this is:
>
> 	VAR + value < VAR
>
> Notably, this is considered "undefined behavior" for signed and pointer
> types, which the kernel works around by using the -fno-strict-overflow
> option in the build[1] (which used to just be -fwrapv). Regardless, we
> want to get the kernel source to the position where we can meaningfully
> instrument arithmetic wrap-around conditions and catch them when they
> are unexpected, regardless of whether they are signed[2], unsigned[3],
> or pointer[4] types.
>
> Refactor open-coded wrap-around addition test to use add_would_overflow().
> This paves the way to enabling the wrap-around sanitizers in the future.
>
> Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
> Link: https://github.com/KSPP/linux/issues/26 [2]
> Link: https://github.com/KSPP/linux/issues/27 [3]
> Link: https://github.com/KSPP/linux/issues/344 [4]
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Oliver Upton <oliver.upton@linux.dev>
> Cc: James Morse <james.morse@arm.com>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Zenghui Yu <yuzenghui@huawei.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: kvmarm@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
>  arch/arm64/kvm/vgic/vgic-mmio-v3.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> index c15ee1df036a..860b774c0c13 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> @@ -863,7 +863,7 @@ static int vgic_v3_alloc_redist_region(struct kvm *kvm, uint32_t index,
>  	int ret;
>  
>  	/* cross the end of memory ? */
> -	if (base + size < base)
> +	if (add_would_overflow(base, size))
>  		return -EINVAL;
>  
>  	if (list_empty(rd_regions)) {


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