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[PATCH 1/2] i386: assert 'cs->kvm_state' is not null
From: |
Vitaly Kuznetsov |
Subject: |
[PATCH 1/2] i386: assert 'cs->kvm_state' is not null |
Date: |
Fri, 16 Jul 2021 13:58:51 +0200 |
Coverity reports potential NULL pointer dereference in
get_supported_hv_cpuid_legacy() when 'cs->kvm_state' is NULL. While
'cs->kvm_state' can indeed be NULL in hv_cpuid_get_host(),
kvm_hyperv_expand_features() makes sure that it only happens when
KVM_CAP_SYS_HYPERV_CPUID is supported and KVM_CAP_SYS_HYPERV_CPUID
implies KVM_CAP_HYPERV_CPUID so get_supported_hv_cpuid_legacy() is
never really called. Add asserts to strengthen the protection against
broken KVM behavior.
Coverity: CID 1458243
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
target/i386/kvm/kvm.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 59ed8327ac13..e69abe48e3f8 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -974,6 +974,12 @@ static struct kvm_cpuid2 *get_supported_hv_cpuid(CPUState
*cs)
do_sys_ioctl =
kvm_check_extension(kvm_state, KVM_CAP_SYS_HYPERV_CPUID) > 0;
+ /*
+ * Non-empty KVM context is needed when KVM_CAP_SYS_HYPERV_CPUID is
+ * unsupported, kvm_hyperv_expand_features() checks for that.
+ */
+ assert(do_sys_ioctl || cs->kvm_state);
+
/*
* When the buffer is too small, KVM_GET_SUPPORTED_HV_CPUID fails with
* -E2BIG, however, it doesn't report back the right size. Keep increasing
@@ -1105,6 +1111,14 @@ static uint32_t hv_cpuid_get_host(CPUState *cs, uint32_t
func, int reg)
if (kvm_check_extension(kvm_state, KVM_CAP_HYPERV_CPUID) > 0) {
cpuid = get_supported_hv_cpuid(cs);
} else {
+ /*
+ * 'cs->kvm_state' may be NULL when Hyper-V features are expanded
+ * before KVM context is created but this is only done when
+ * KVM_CAP_SYS_HYPERV_CPUID is supported and it implies
+ * KVM_CAP_HYPERV_CPUID.
+ */
+ assert(cs->kvm_state);
+
cpuid = get_supported_hv_cpuid_legacy(cs);
}
hv_cpuid_cache = cpuid;
--
2.31.1
- [PATCH 1/2] i386: assert 'cs->kvm_state' is not null,
Vitaly Kuznetsov <=