From 8b9e13d2de73b5513c2ceffe0f62eab40206a126 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Thu, 8 Dec 2022 11:27:00 +0100 Subject: [PATCH] KVM: x86: hyper-v: Fix 'using uninitialized value' Coverity warning In kvm_hv_flush_tlb(), 'data_offset' and 'consumed_xmm_halves' variables are used in a mutually exclusive way: in 'hc->fast' we count in 'XMM halves' and increase 'data_offset' otherwise. Coverity discovered, that in one case both variables are incremented unconditionally. This doesn't seem to cause any issues as the only user of 'data_offset'/'consumed_xmm_halves' data is kvm_hv_get_tlb_flush_entries() -> kvm_hv_get_hc_data() which also takes into account 'hc->fast' but is still worth fixing. To make things explicit, put 'data_offset' and 'consumed_xmm_halves' to 'struct kvm_hv_hcall' as a union and use at call sites. This allows to remove explicit 'data_offset'/'consumed_xmm_halves' parameters from kvm_hv_get_hc_data()/kvm_get_sparse_vp_set()/kvm_hv_get_tlb_flush_entries() helpers. Note: 'struct kvm_hv_hcall' is allocated on stack in kvm_hv_hypercall() and is not zeroed, consumers are supposed to initialize the appropriate field if needed. Reported-by: coverity-bot Addresses-Coverity-ID: 1527764 ("Uninitialized variables") Fixes: 260970862c88 ("KVM: x86: hyper-v: Handle HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} calls gently") Signed-off-by: Vitaly Kuznetsov Reviewed-by: Sean Christopherson Message-Id: <20221208102700.959630-1-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/hyperv.c | 63 +++++++++++++++++++++++++++++---------------------- 1 file changed, 36 insertions(+), 27 deletions(-) diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 2c7f2a2..e829694 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -1769,6 +1769,7 @@ static bool hv_is_vp_in_sparse_set(u32 vp_id, u64 valid_bank_mask, u64 sparse_ba } struct kvm_hv_hcall { + /* Hypercall input data */ u64 param; u64 ingpa; u64 outgpa; @@ -1779,12 +1780,21 @@ struct kvm_hv_hcall { bool fast; bool rep; sse128_t xmm[HV_HYPERCALL_MAX_XMM_REGISTERS]; + + /* + * Current read offset when KVM reads hypercall input data gradually, + * either offset in bytes from 'ingpa' for regular hypercalls or the + * number of already consumed 'XMM halves' for 'fast' hypercalls. + */ + union { + gpa_t data_offset; + int consumed_xmm_halves; + }; }; static int kvm_hv_get_hc_data(struct kvm *kvm, struct kvm_hv_hcall *hc, - u16 orig_cnt, u16 cnt_cap, u64 *data, - int consumed_xmm_halves, gpa_t offset) + u16 orig_cnt, u16 cnt_cap, u64 *data) { /* * Preserve the original count when ignoring entries via a "cap", KVM @@ -1799,11 +1809,11 @@ static int kvm_hv_get_hc_data(struct kvm *kvm, struct kvm_hv_hcall *hc, * Each XMM holds two sparse banks, but do not count halves that * have already been consumed for hypercall parameters. */ - if (orig_cnt > 2 * HV_HYPERCALL_MAX_XMM_REGISTERS - consumed_xmm_halves) + if (orig_cnt > 2 * HV_HYPERCALL_MAX_XMM_REGISTERS - hc->consumed_xmm_halves) return HV_STATUS_INVALID_HYPERCALL_INPUT; for (i = 0; i < cnt; i++) { - j = i + consumed_xmm_halves; + j = i + hc->consumed_xmm_halves; if (j % 2) data[i] = sse128_hi(hc->xmm[j / 2]); else @@ -1812,27 +1822,24 @@ static int kvm_hv_get_hc_data(struct kvm *kvm, struct kvm_hv_hcall *hc, return 0; } - return kvm_read_guest(kvm, hc->ingpa + offset, data, + return kvm_read_guest(kvm, hc->ingpa + hc->data_offset, data, cnt * sizeof(*data)); } static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc, - u64 *sparse_banks, int consumed_xmm_halves, - gpa_t offset) + u64 *sparse_banks) { if (hc->var_cnt > HV_MAX_SPARSE_VCPU_BANKS) return -EINVAL; /* Cap var_cnt to ignore banks that cannot contain a legal VP index. */ return kvm_hv_get_hc_data(kvm, hc, hc->var_cnt, KVM_HV_MAX_SPARSE_VCPU_SET_BITS, - sparse_banks, consumed_xmm_halves, offset); + sparse_banks); } -static int kvm_hv_get_tlb_flush_entries(struct kvm *kvm, struct kvm_hv_hcall *hc, u64 entries[], - int consumed_xmm_halves, gpa_t offset) +static int kvm_hv_get_tlb_flush_entries(struct kvm *kvm, struct kvm_hv_hcall *hc, u64 entries[]) { - return kvm_hv_get_hc_data(kvm, hc, hc->rep_cnt, hc->rep_cnt, - entries, consumed_xmm_halves, offset); + return kvm_hv_get_hc_data(kvm, hc, hc->rep_cnt, hc->rep_cnt, entries); } static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu, @@ -1926,8 +1933,6 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) struct kvm_vcpu *v; unsigned long i; bool all_cpus; - int consumed_xmm_halves = 0; - gpa_t data_offset; /* * The Hyper-V TLFS doesn't allow more than HV_MAX_SPARSE_VCPU_BANKS @@ -1955,12 +1960,12 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) flush.address_space = hc->ingpa; flush.flags = hc->outgpa; flush.processor_mask = sse128_lo(hc->xmm[0]); - consumed_xmm_halves = 1; + hc->consumed_xmm_halves = 1; } else { if (unlikely(kvm_read_guest(kvm, hc->ingpa, &flush, sizeof(flush)))) return HV_STATUS_INVALID_HYPERCALL_INPUT; - data_offset = sizeof(flush); + hc->data_offset = sizeof(flush); } trace_kvm_hv_flush_tlb(flush.processor_mask, @@ -1985,12 +1990,12 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) flush_ex.flags = hc->outgpa; memcpy(&flush_ex.hv_vp_set, &hc->xmm[0], sizeof(hc->xmm[0])); - consumed_xmm_halves = 2; + hc->consumed_xmm_halves = 2; } else { if (unlikely(kvm_read_guest(kvm, hc->ingpa, &flush_ex, sizeof(flush_ex)))) return HV_STATUS_INVALID_HYPERCALL_INPUT; - data_offset = sizeof(flush_ex); + hc->data_offset = sizeof(flush_ex); } trace_kvm_hv_flush_tlb_ex(flush_ex.hv_vp_set.valid_bank_mask, @@ -2009,8 +2014,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) if (!hc->var_cnt) goto ret_success; - if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks, - consumed_xmm_halves, data_offset)) + if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks)) return HV_STATUS_INVALID_HYPERCALL_INPUT; } @@ -2021,8 +2025,10 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) * consumed_xmm_halves to make sure TLB flush entries are read * from the correct offset. */ - data_offset += hc->var_cnt * sizeof(sparse_banks[0]); - consumed_xmm_halves += hc->var_cnt; + if (hc->fast) + hc->consumed_xmm_halves += hc->var_cnt; + else + hc->data_offset += hc->var_cnt * sizeof(sparse_banks[0]); } if (hc->code == HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE || @@ -2030,8 +2036,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) hc->rep_cnt > ARRAY_SIZE(__tlb_flush_entries)) { tlb_flush_entries = NULL; } else { - if (kvm_hv_get_tlb_flush_entries(kvm, hc, __tlb_flush_entries, - consumed_xmm_halves, data_offset)) + if (kvm_hv_get_tlb_flush_entries(kvm, hc, __tlb_flush_entries)) return HV_STATUS_INVALID_HYPERCALL_INPUT; tlb_flush_entries = __tlb_flush_entries; } @@ -2180,9 +2185,13 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) if (!hc->var_cnt) goto ret_success; - if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks, 1, - offsetof(struct hv_send_ipi_ex, - vp_set.bank_contents))) + if (!hc->fast) + hc->data_offset = offsetof(struct hv_send_ipi_ex, + vp_set.bank_contents); + else + hc->consumed_xmm_halves = 1; + + if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks)) return HV_STATUS_INVALID_HYPERCALL_INPUT; } -- 2.7.4