diff options
| -rw-r--r-- | executor/common_kvm_amd64_syzos.h | 28 | ||||
| -rw-r--r-- | sys/linux/dev_kvm_amd64.txt | 61 | ||||
| -rw-r--r-- | sys/linux/test/amd64-syz_kvm_nested_vmwrite_mask | 40 |
3 files changed, 114 insertions, 15 deletions
diff --git a/executor/common_kvm_amd64_syzos.h b/executor/common_kvm_amd64_syzos.h index a691bebde..ea9aec800 100644 --- a/executor/common_kvm_amd64_syzos.h +++ b/executor/common_kvm_amd64_syzos.h @@ -31,6 +31,7 @@ typedef enum { SYZOS_API_NESTED_LOAD_CODE = 302, SYZOS_API_NESTED_VMLAUNCH = 303, SYZOS_API_NESTED_VMRESUME = 304, + SYZOS_API_NESTED_INTEL_VMWRITE_MASK = 340, SYZOS_API_STOP, // Must be the last one } syzos_api_id; @@ -76,6 +77,11 @@ struct api_call_3 { uint64 args[3]; }; +struct api_call_5 { + struct api_call_header header; + uint64 args[5]; +}; + // This struct must match the push/pop order in nested_vm_exit_handler_intel_asm(). struct l2_guest_regs { uint64 rax, rbx, rcx, rdx, rsi, rdi, rbp; @@ -104,6 +110,7 @@ GUEST_CODE static void guest_handle_nested_create_vm(struct api_call_1* cmd, uin GUEST_CODE static void guest_handle_nested_load_code(struct api_call_nested_load_code* cmd, uint64 cpu_id); GUEST_CODE static void guest_handle_nested_vmlaunch(struct api_call_1* cmd, uint64 cpu_id); GUEST_CODE static void guest_handle_nested_vmresume(struct api_call_1* cmd, uint64 cpu_id); +GUEST_CODE static void guest_handle_nested_intel_vmwrite_mask(struct api_call_5* cmd, uint64 cpu_id); typedef enum { UEXIT_END = (uint64)-1, @@ -213,6 +220,9 @@ guest_main(uint64 size, uint64 cpu) } else if (call == SYZOS_API_NESTED_VMRESUME) { // Resume a nested VM. guest_handle_nested_vmresume((struct api_call_1*)cmd, cpu); + } else if (call == SYZOS_API_NESTED_INTEL_VMWRITE_MASK) { + // Write to a VMCS field using masks. + guest_handle_nested_intel_vmwrite_mask((struct api_call_5*)cmd, cpu); } addr += cmd->size; size -= cmd->size; @@ -1228,4 +1238,22 @@ guest_handle_nested_vmresume(struct api_call_1* cmd, uint64 cpu_id) } } +GUEST_CODE static noinline void +guest_handle_nested_intel_vmwrite_mask(struct api_call_5* cmd, uint64 cpu_id) +{ + if (get_cpu_vendor() != CPU_VENDOR_INTEL) + return; + uint64 vm_id = cmd->args[0]; + nested_vmptrld(cpu_id, vm_id); + uint64 field = cmd->args[1]; + uint64 set_mask = cmd->args[2]; + uint64 unset_mask = cmd->args[3]; + uint64 flip_mask = cmd->args[4]; + + uint64 current_value = vmread(field); + uint64 new_value = (current_value & ~unset_mask) | set_mask; + new_value ^= flip_mask; + vmwrite(field, new_value); +} + #endif // EXECUTOR_COMMON_KVM_AMD64_SYZOS_H diff --git a/sys/linux/dev_kvm_amd64.txt b/sys/linux/dev_kvm_amd64.txt index d3dac2cf9..29dab16e4 100644 --- a/sys/linux/dev_kvm_amd64.txt +++ b/sys/linux/dev_kvm_amd64.txt @@ -101,23 +101,54 @@ syzos_api_nested_load_code { insns text[x86_64] } [packed] +# VMCS Component Encoding is a 32-bit value, but only bits 0:15 are used. +# Certain bit combinations are invalid, because the number encodes additional +# parameters like access type and width. +# Constants as per Intel SDM vol. 3C, Appendix B. +vmcs_field_encoding [ + control16 int64[0x0:0x4, 2] + guest16 int64[0x800:0x812, 2] + host16 int64[0xc00:0xc0c, 2] + control64 int64[0x2000:0x2033] + ro64 int64[0x2400:0x2401] + guest64 int64[0x2800:0x2813] + host64 int64[0x2c00:0x2c05] + control32 int64[0x4000:0x4022, 2] + ro32 int64[0x4400:0x440e, 2] + guest32 int64[0x4800:0x482e, 2] + host32 int64[0x4c00:0x4c00] + control_nat int64[0x6000:0x600e, 2] + ro_nat int64[0x6400:0x640a, 2] + guest_nat int64[0x6800:0x6826, 2] + host_nat int64[0x6c00:0x6c16, 2] +] + +syzos_api_nested_intel_vmwrite_mask { + vm_id syzos_api_vm_id + field vmcs_field_encoding + set_mask int64 + unset_mask int64 + flip_mask int64 +} + # IDs here must match those in executor/common_kvm_amd64_syzos.h. syzos_api_call$x86 [ - uexit syzos_api$x86[0, intptr] - code syzos_api$x86[10, syzos_api_code$x86] - cpuid syzos_api$x86[100, syzos_api_cpuid] - wrmsr syzos_api$x86[101, syzos_api_wrmsr] - rdmsr syzos_api$x86[102, syzos_api_rdmsr] - wr_crn syzos_api$x86[103, syzos_api_wr_crn] - wr_drn syzos_api$x86[104, syzos_api_wr_drn] - in_dx syzos_api$x86[105, syzos_api_in_dx] - out_dx syzos_api$x86[106, syzos_api_out_dx] - set_irq_handler syzos_api$x86[200, syzos_api_set_irq_handler] - enable_nested syzos_api$x86[300, const[0, intptr]] - nested_create_vm syzos_api$x86[301, syzos_api_vm_id] - nested_load_code syzos_api$x86[302, syzos_api_nested_load_code] - nested_vmlaunch syzos_api$x86[303, syzos_api_vm_id] - nested_vmresume syzos_api$x86[304, syzos_api_vm_id] + uexit syzos_api$x86[0, intptr] + code syzos_api$x86[10, syzos_api_code$x86] + cpuid syzos_api$x86[100, syzos_api_cpuid] + wrmsr syzos_api$x86[101, syzos_api_wrmsr] + rdmsr syzos_api$x86[102, syzos_api_rdmsr] + wr_crn syzos_api$x86[103, syzos_api_wr_crn] + wr_drn syzos_api$x86[104, syzos_api_wr_drn] + in_dx syzos_api$x86[105, syzos_api_in_dx] + out_dx syzos_api$x86[106, syzos_api_out_dx] + set_irq_handler syzos_api$x86[200, syzos_api_set_irq_handler] + enable_nested syzos_api$x86[300, const[0, intptr]] + nested_create_vm syzos_api$x86[301, syzos_api_vm_id] + nested_load_code syzos_api$x86[302, syzos_api_nested_load_code] + nested_vmlaunch syzos_api$x86[303, syzos_api_vm_id] + nested_vmresume syzos_api$x86[304, syzos_api_vm_id] + nested_intel_vmwrite_mask syzos_api$x86[340, syzos_api_nested_intel_vmwrite_mask] ] [varlen] kvm_text_x86 [ diff --git a/sys/linux/test/amd64-syz_kvm_nested_vmwrite_mask b/sys/linux/test/amd64-syz_kvm_nested_vmwrite_mask new file mode 100644 index 000000000..66efb98f8 --- /dev/null +++ b/sys/linux/test/amd64-syz_kvm_nested_vmwrite_mask @@ -0,0 +1,40 @@ +# +# requires: arch=amd64 -threaded +# +r0 = openat$kvm(0, &AUTO='/dev/kvm\x00', 0x0, 0x0) +r1 = ioctl$KVM_CREATE_VM(r0, AUTO, 0x0) +r2 = syz_kvm_setup_syzos_vm$x86(r1, &(0x7f0000c00000/0x400000)=nil) + +# Create a nested VM that performs HLT and INVD. +# 1. L2 executes HLT -> exit to L1. +# 2. L1 disables HLT exiting via vmwrite to CPU_BASED_VM_EXEC_CONTROL. +# 3. L1 resumes L2 (RIP still at HLT). +# 4. L2 executes HLT (no exit), which is delivered to L0. +# 5. L0 resumes L1, which is still running L2. +# 6. L2 executes INVD -> exit to L1. +# +r3 = syz_kvm_add_vcpu$x86(r2, &AUTO={0x0, &AUTO=[@enable_nested={AUTO, AUTO, 0x0}, @nested_create_vm={AUTO, AUTO, 0x0}, @nested_load_code={AUTO, AUTO, {0x0, "f40f08"}}, @nested_vmlaunch={AUTO, AUTO, 0x0}, @nested_intel_vmwrite_mask={AUTO, AUTO, {0x0, @control32=0x4002, 0x0, 0x80, 0x0}}, @nested_vmresume={AUTO, AUTO, 0x0}], AUTO}) +r4 = ioctl$KVM_GET_VCPU_MMAP_SIZE(r0, AUTO) +r5 = mmap$KVM_VCPU(&(0x7f0000009000/0x1000)=nil, r4, 0x3, 0x1, r3, 0x0) + +# L2 VM executes HLT. Exit reason is mapped to 0xe2e20001. +# +ioctl$KVM_RUN(r3, AUTO, 0x0) +syz_kvm_assert_syzos_uexit$x86(r5, 0xe2e20001) + +# L1 disables HLT exiting and resumes L2. L2 resumes at HLT, and breaks out of KVM_RUN. +# 0x05 is KVM_EXIT_HLT. +# This confirms that the vmwrite command to disable HLT exiting was successful. +# +ioctl$KVM_RUN(r3, AUTO, 0x0) +syz_kvm_assert_syzos_kvm_exit$x86(r5, 0x5) + +# After resuming, L2 executes INVD. Exit reason is mapped to 0xe2e20002. +# +ioctl$KVM_RUN(r3, AUTO, 0x0) +syz_kvm_assert_syzos_uexit$x86(r5, 0xe2e20002) + +# guest_main should finish with guest_uexit(-1). +# +ioctl$KVM_RUN(r3, AUTO, 0x0) +syz_kvm_assert_syzos_uexit$x86(r5, 0xffffffff) |