| Message ID | 20240123002814.1396804-24-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | overflow: Refactor open-coded arithmetic wrap-around | expand |
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.
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. >
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;
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(-)