31b1f3b60a
fault delivery (XSA-156) CVE-2015-5307-xsa156.patch OBS-URL: https://build.opensuse.org/package/show/Virtualization/xen?expand=0&rev=385
130 lines
4.9 KiB
Diff
130 lines
4.9 KiB
Diff
References: bsc#953527 CVE-2015-5307 XSA-156
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x86/HVM: always intercept #AC and #DB
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Both being benign exceptions, and both being possible to get triggered
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by exception delivery, this is required to prevent a guest from locking
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up a CPU (resulting from no other VM exits occurring once getting into
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such a loop).
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The specific scenarios:
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1) #AC may be raised during exception delivery if the handler is set to
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be a ring-3 one by a 32-bit guest, and the stack is misaligned.
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2) #DB may be raised during exception delivery when a breakpoint got
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placed on a data structure involved in delivering the exception. This
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can result in an endless loop when a 64-bit guest uses a non-zero IST
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for the vector 1 IDT entry, but even without use of IST the time it
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takes until a contributory fault would get raised (results depending
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on the handler) may be quite long.
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This is XSA-156.
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Reported-by: Benjamin Serebrin <serebrin@google.com>
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Signed-off-by: Jan Beulich <jbeulich@suse.com>
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Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Tested-by: Andrew Cooper <andrew.cooper3@citrix.com>
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--- a/xen/arch/x86/hvm/svm/svm.c
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+++ b/xen/arch/x86/hvm/svm/svm.c
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@@ -1045,10 +1045,11 @@ static void noreturn svm_do_resume(struc
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unlikely(v->arch.hvm_vcpu.debug_state_latch != debug_state) )
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{
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uint32_t intercepts = vmcb_get_exception_intercepts(vmcb);
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- uint32_t mask = (1U << TRAP_debug) | (1U << TRAP_int3);
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+
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v->arch.hvm_vcpu.debug_state_latch = debug_state;
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vmcb_set_exception_intercepts(
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- vmcb, debug_state ? (intercepts | mask) : (intercepts & ~mask));
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+ vmcb, debug_state ? (intercepts | (1U << TRAP_int3))
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+ : (intercepts & ~(1U << TRAP_int3)));
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}
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if ( v->arch.hvm_svm.launch_core != smp_processor_id() )
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@@ -2435,8 +2436,9 @@ void svm_vmexit_handler(struct cpu_user_
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case VMEXIT_EXCEPTION_DB:
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if ( !v->domain->debugger_attached )
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- goto unexpected_exit_type;
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- domain_pause_for_debugger();
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+ hvm_inject_hw_exception(TRAP_debug, HVM_DELIVER_NO_ERROR_CODE);
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+ else
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+ domain_pause_for_debugger();
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break;
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case VMEXIT_EXCEPTION_BP:
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@@ -2484,6 +2486,11 @@ void svm_vmexit_handler(struct cpu_user_
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break;
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}
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+ case VMEXIT_EXCEPTION_AC:
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+ HVMTRACE_1D(TRAP, TRAP_alignment_check);
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+ hvm_inject_hw_exception(TRAP_alignment_check, vmcb->exitinfo1);
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+ break;
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+
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case VMEXIT_EXCEPTION_UD:
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svm_vmexit_ud_intercept(regs);
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break;
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--- a/xen/arch/x86/hvm/vmx/vmx.c
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+++ b/xen/arch/x86/hvm/vmx/vmx.c
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@@ -1186,16 +1186,10 @@ static void vmx_update_host_cr3(struct v
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void vmx_update_debug_state(struct vcpu *v)
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{
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- unsigned long mask;
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-
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- mask = 1u << TRAP_int3;
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- if ( !cpu_has_monitor_trap_flag )
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- mask |= 1u << TRAP_debug;
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-
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if ( v->arch.hvm_vcpu.debug_state_latch )
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- v->arch.hvm_vmx.exception_bitmap |= mask;
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+ v->arch.hvm_vmx.exception_bitmap |= 1U << TRAP_int3;
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else
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- v->arch.hvm_vmx.exception_bitmap &= ~mask;
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+ v->arch.hvm_vmx.exception_bitmap &= ~(1U << TRAP_int3);
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vmx_vmcs_enter(v);
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vmx_update_exception_bitmap(v);
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@@ -2801,9 +2795,10 @@ void vmx_vmexit_handler(struct cpu_user_
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__vmread(EXIT_QUALIFICATION, &exit_qualification);
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HVMTRACE_1D(TRAP_DEBUG, exit_qualification);
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write_debugreg(6, exit_qualification | 0xffff0ff0);
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- if ( !v->domain->debugger_attached || cpu_has_monitor_trap_flag )
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- goto exit_and_crash;
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- domain_pause_for_debugger();
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+ if ( !v->domain->debugger_attached )
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+ hvm_inject_hw_exception(vector, HVM_DELIVER_NO_ERROR_CODE);
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+ else
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+ domain_pause_for_debugger();
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break;
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case TRAP_int3:
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{
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@@ -2868,6 +2863,11 @@ void vmx_vmexit_handler(struct cpu_user_
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hvm_inject_page_fault(regs->error_code, exit_qualification);
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break;
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+ case TRAP_alignment_check:
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+ HVMTRACE_1D(TRAP, vector);
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+ __vmread(VM_EXIT_INTR_ERROR_CODE, &ecode);
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+ hvm_inject_hw_exception(vector, ecode);
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+ break;
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case TRAP_nmi:
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if ( (intr_info & INTR_INFO_INTR_TYPE_MASK) !=
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(X86_EVENTTYPE_NMI << 8) )
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--- a/xen/include/asm-x86/hvm/hvm.h
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+++ b/xen/include/asm-x86/hvm/hvm.h
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@@ -378,7 +378,10 @@ static inline int hvm_event_pending(stru
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(X86_CR4_VMXE | X86_CR4_PAE | X86_CR4_MCE))
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/* These exceptions must always be intercepted. */
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-#define HVM_TRAP_MASK ((1U << TRAP_machine_check) | (1U << TRAP_invalid_op))
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+#define HVM_TRAP_MASK ((1U << TRAP_debug) | \
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+ (1U << TRAP_invalid_op) | \
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+ (1U << TRAP_alignment_check) | \
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+ (1U << TRAP_machine_check))
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/*
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* x86 event types. This enumeration is valid for:
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