We do direct useraccess copying to the kvm_cpu_context structure
embedded in the kvm_vcpu_arch structure, and to the vcpu debug register
state. Everything else (timer, PMU, vgic) goes through a temporary
indirection.
Fixing all accesses to kvm_cpu_context is massively invasive, and we'd
like to avoid that, so we tell kvm_init_usercopy to whitelist accesses
to out context structure.
The debug system register accesses on arm64 are modified to work through
an indirection instead.
Cc: kernel-hardening@xxxxxxxxxxxxxxxxxx
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
---
This fixes KVM/ARM on today's linux next with CONFIG_HARDENED_USERCOPY.
The patch is based on linux-next plus Paolo's x86 patch which introduces
kvm_init_usercopy. Not sure how this needs to get merged, but it would
potentially make sense for Paolo to put together a set of the patches
needed for this.
Thanks,
-Christoffer
arch/arm64/kvm/sys_regs.c | 36 ++++++++++++++++++++----------------
virt/kvm/arm/arm.c | 5 ++++-
2 files changed, 24 insertions(+), 17 deletions(-)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 2e070d3baf9f..cdf47a9108fe 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -293,19 +293,20 @@ static bool trap_bvr(struct kvm_vcpu *vcpu,
static int set_bvr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- __u64 *r = &vcpu->arch.vcpu_debug_state.dbg_bvr[rd->reg];
+ __u64 r;
- if (copy_from_user(r, uaddr, KVM_REG_SIZE(reg->id)) != 0)
+ if (copy_from_user(&r, uaddr, KVM_REG_SIZE(reg->id)) != 0)
return -EFAULT;
+ vcpu->arch.vcpu_debug_state.dbg_bvr[rd->reg] = r;
return 0;
}
static int get_bvr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- __u64 *r = &vcpu->arch.vcpu_debug_state.dbg_bvr[rd->reg];
+ __u64 r = vcpu->arch.vcpu_debug_state.dbg_bvr[rd->reg];
- if (copy_to_user(uaddr, r, KVM_REG_SIZE(reg->id)) != 0)
+ if (copy_to_user(uaddr, &r, KVM_REG_SIZE(reg->id)) != 0)
return -EFAULT;
return 0;
}
@@ -335,10 +336,11 @@ static bool trap_bcr(struct kvm_vcpu *vcpu,
static int set_bcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- __u64 *r = &vcpu->arch.vcpu_debug_state.dbg_bcr[rd->reg];
+ __u64 r;
- if (copy_from_user(r, uaddr, KVM_REG_SIZE(reg->id)) != 0)
+ if (copy_from_user(&r, uaddr, KVM_REG_SIZE(reg->id)) != 0)
return -EFAULT;
+ vcpu->arch.vcpu_debug_state.dbg_bcr[rd->reg] = r;
return 0;
}
@@ -346,9 +348,9 @@ static int set_bcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
static int get_bcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- __u64 *r = &vcpu->arch.vcpu_debug_state.dbg_bcr[rd->reg];
+ __u64 r = vcpu->arch.vcpu_debug_state.dbg_bcr[rd->reg];
- if (copy_to_user(uaddr, r, KVM_REG_SIZE(reg->id)) != 0)
+ if (copy_to_user(uaddr, &r, KVM_REG_SIZE(reg->id)) != 0)
return -EFAULT;
return 0;
}
@@ -379,19 +381,20 @@ static bool trap_wvr(struct kvm_vcpu *vcpu,
static int set_wvr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- __u64 *r = &vcpu->arch.vcpu_debug_state.dbg_wvr[rd->reg];
+ __u64 r;
- if (copy_from_user(r, uaddr, KVM_REG_SIZE(reg->id)) != 0)
+ if (copy_from_user(&r, uaddr, KVM_REG_SIZE(reg->id)) != 0)
return -EFAULT;
+ vcpu->arch.vcpu_debug_state.dbg_wvr[rd->reg] = r;
return 0;
}
static int get_wvr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- __u64 *r = &vcpu->arch.vcpu_debug_state.dbg_wvr[rd->reg];
+ __u64 r = vcpu->arch.vcpu_debug_state.dbg_wvr[rd->reg];
- if (copy_to_user(uaddr, r, KVM_REG_SIZE(reg->id)) != 0)
+ if (copy_to_user(uaddr, &r, KVM_REG_SIZE(reg->id)) != 0)
return -EFAULT;
return 0;
}
@@ -421,19 +424,20 @@ static bool trap_wcr(struct kvm_vcpu *vcpu,
static int set_wcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- __u64 *r = &vcpu->arch.vcpu_debug_state.dbg_wcr[rd->reg];
+ __u64 r;
- if (copy_from_user(r, uaddr, KVM_REG_SIZE(reg->id)) != 0)
+ if (copy_from_user(&r, uaddr, KVM_REG_SIZE(reg->id)) != 0)
return -EFAULT;
+ vcpu->arch.vcpu_debug_state.dbg_wcr[rd->reg] = r;
return 0;
}
static int get_wcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- __u64 *r = &vcpu->arch.vcpu_debug_state.dbg_wcr[rd->reg];
+ __u64 r = vcpu->arch.vcpu_debug_state.dbg_wcr[rd->reg];
- if (copy_to_user(uaddr, r, KVM_REG_SIZE(reg->id)) != 0)
+ if (copy_to_user(uaddr, &r, KVM_REG_SIZE(reg->id)) != 0)
return -EFAULT;
return 0;
}
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index b9f68e4add71..639e388678ff 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1502,7 +1502,10 @@ void kvm_arch_exit(void)
static int arm_init(void)
{
- int rc = kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE);
+ int rc = kvm_init_usercopy(NULL, sizeof(struct kvm_vcpu), 0,
+ offsetof(struct kvm_vcpu_arch, ctxt),
+ sizeof_field(struct kvm_vcpu_arch, ctxt),
+ THIS_MODULE);
return rc;
}
--
2.14.2
