[PATCH 5.15 178/207] KVM: SEV: Return appropriate error codes if SEV-ES scratch setup fails

Greg Kroah-Hartman
2021-12-06T15:53:45Z

From: Sean Christopherson <seanjc@google.com>

[ Upstream commit 75236f5f2299b502e4b9b267c1ce3bc14a222ceb ]

Return appropriate error codes if setting up the GHCB scratch area for an
SEV-ES guest fails. In particular, returning -EINVAL instead of -ENOMEM
when allocating the kernel buffer could be confusing as userspace would
likely suspect a guest issue.

Fixes: 8f423a80d299 ("KVM: SVM: Support MMIO for an SEV-ES guest")
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211109222350.2266045-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/svm/sev.c | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index ca0effb79eab9..134c4ea5e6ad8 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2317,7 +2317,7 @@ void pre_sev_run(struct vcpu_svm *svm, int cpu)
}

#define GHCB_SCRATCH_AREA_LIMIT (16ULL * PAGE_SIZE)
-static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
+static int setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
{
struct vmcb_control_area *control = &svm->vmcb->control;
struct ghcb *ghcb = svm->ghcb;
@@ -2328,14 +2328,14 @@ static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
scratch_gpa_beg = ghcb_get_sw_scratch(ghcb);
if (!scratch_gpa_beg) {
pr_err("vmgexit: scratch gpa not provided\n");
- return false;
+ return -EINVAL;
}

scratch_gpa_end = scratch_gpa_beg + len;
if (scratch_gpa_end < scratch_gpa_beg) {
pr_err("vmgexit: scratch length (%#llx) not valid for scratch address (%#llx)\n",
len, scratch_gpa_beg);
- return false;
+ return -EINVAL;
}

if ((scratch_gpa_beg & PAGE_MASK) == control->ghcb_gpa) {
@@ -2353,7 +2353,7 @@ static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
scratch_gpa_end > ghcb_scratch_end) {
pr_err("vmgexit: scratch area is outside of GHCB shared buffer area (%#llx - %#llx)\n",
scratch_gpa_beg, scratch_gpa_end);
- return false;
+ return -EINVAL;
}

scratch_va = (void *)svm->ghcb;
@@ -2366,18 +2366,18 @@ static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
if (len > GHCB_SCRATCH_AREA_LIMIT) {
pr_err("vmgexit: scratch area exceeds KVM limits (%#llx requested, %#llx limit)\n",
len, GHCB_SCRATCH_AREA_LIMIT);
- return false;
+ return -EINVAL;
}
scratch_va = kzalloc(len, GFP_KERNEL_ACCOUNT);
if (!scratch_va)
- return false;
+ return -ENOMEM;

if (kvm_read_guest(svm->vcpu.kvm, scratch_gpa_beg, scratch_va, len)) {
/* Unable to copy scratch area from guest */
pr_err("vmgexit: kvm_read_guest for scratch area failed\n");

kfree(scratch_va);
- return false;
+ return -EFAULT;
}

/*
@@ -2393,7 +2393,7 @@ static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
svm->ghcb_sa = scratch_va;
svm->ghcb_sa_len = len;

- return true;
+ return 0;
}

static void set_ghcb_msr_bits(struct vcpu_svm *svm, u64 value, u64 mask,
@@ -2532,10 +2532,10 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
ghcb_set_sw_exit_info_1(ghcb, 0);
ghcb_set_sw_exit_info_2(ghcb, 0);

- ret = -EINVAL;
switch (exit_code) {
case SVM_VMGEXIT_MMIO_READ:
- if (!setup_vmgexit_scratch(svm, true, control->exit_info_2))
+ ret = setup_vmgexit_scratch(svm, true, control->exit_info_2);
+ if (ret)
break;

ret = kvm_sev_es_mmio_read(vcpu,
@@ -2544,7 +2544,8 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
svm->ghcb_sa);
break;
case SVM_VMGEXIT_MMIO_WRITE:
- if (!setup_vmgexit_scratch(svm, false, control->exit_info_2))
+ ret = setup_vmgexit_scratch(svm, false, control->exit_info_2);
+ if (ret)
break;

ret = kvm_sev_es_mmio_write(vcpu,
@@ -2587,6 +2588,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
vcpu_unimpl(vcpu,
"vmgexit: unsupported event - exit_info_1=%#llx, exit_info_2=%#llx\n",
control->exit_info_1, control->exit_info_2);
+ ret = -EINVAL;
break;
default:
ret = svm_invoke_exit_handler(vcpu, exit_code);
@@ -2599,6 +2601,7 @@ int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in)
{
int count;
int bytes;
+ int r;

if (svm->vmcb->control.exit_info_2 > INT_MAX)
return -EINVAL;
@@ -2607,8 +2610,9 @@ int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in)
if (unlikely(check_mul_overflow(count, size, &bytes)))
return -EINVAL;

- if (!setup_vmgexit_scratch(svm, in, bytes))
- return -EINVAL;
+ r = setup_vmgexit_scratch(svm, in, bytes);
+ if (r)
+ return r;

return kvm_sev_es_string_io(&svm->vcpu, size, port, svm->ghcb_sa, count, in);
}
--
2.33.0