gsd-2021-47092
Vulnerability from gsd
Modified
2024-03-01 06:04
Details
In the Linux kernel, the following vulnerability has been resolved:
KVM: VMX: Always clear vmx->fail on emulation_required
Revert a relatively recent change that set vmx->fail if the vCPU is in L2
and emulation_required is true, as that behavior is completely bogus.
Setting vmx->fail and synthesizing a VM-Exit is contradictory and wrong:
(a) it's impossible to have both a VM-Fail and VM-Exit
(b) vmcs.EXIT_REASON is not modified on VM-Fail
(c) emulation_required refers to guest state and guest state checks are
always VM-Exits, not VM-Fails.
For KVM specifically, emulation_required is handled before nested exits
in __vmx_handle_exit(), thus setting vmx->fail has no immediate effect,
i.e. KVM calls into handle_invalid_guest_state() and vmx->fail is ignored.
Setting vmx->fail can ultimately result in a WARN in nested_vmx_vmexit()
firing when tearing down the VM as KVM never expects vmx->fail to be set
when L2 is active, KVM always reflects those errors into L1.
------------[ cut here ]------------
WARNING: CPU: 0 PID: 21158 at arch/x86/kvm/vmx/nested.c:4548
nested_vmx_vmexit+0x16bd/0x17e0
arch/x86/kvm/vmx/nested.c:4547
Modules linked in:
CPU: 0 PID: 21158 Comm: syz-executor.1 Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:nested_vmx_vmexit+0x16bd/0x17e0 arch/x86/kvm/vmx/nested.c:4547
Code: <0f> 0b e9 2e f8 ff ff e8 57 b3 5d 00 0f 0b e9 00 f1 ff ff 89 e9 80
Call Trace:
vmx_leave_nested arch/x86/kvm/vmx/nested.c:6220 [inline]
nested_vmx_free_vcpu+0x83/0xc0 arch/x86/kvm/vmx/nested.c:330
vmx_free_vcpu+0x11f/0x2a0 arch/x86/kvm/vmx/vmx.c:6799
kvm_arch_vcpu_destroy+0x6b/0x240 arch/x86/kvm/x86.c:10989
kvm_vcpu_destroy+0x29/0x90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:441
kvm_free_vcpus arch/x86/kvm/x86.c:11426 [inline]
kvm_arch_destroy_vm+0x3ef/0x6b0 arch/x86/kvm/x86.c:11545
kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1189 [inline]
kvm_put_kvm+0x751/0xe40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1220
kvm_vcpu_release+0x53/0x60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3489
__fput+0x3fc/0x870 fs/file_table.c:280
task_work_run+0x146/0x1c0 kernel/task_work.c:164
exit_task_work include/linux/task_work.h:32 [inline]
do_exit+0x705/0x24f0 kernel/exit.c:832
do_group_exit+0x168/0x2d0 kernel/exit.c:929
get_signal+0x1740/0x2120 kernel/signal.c:2852
arch_do_signal_or_restart+0x9c/0x730 arch/x86/kernel/signal.c:868
handle_signal_work kernel/entry/common.c:148 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x191/0x220 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x2e/0x70 kernel/entry/common.c:300
do_syscall_64+0x53/0xd0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae
Aliases
{ "gsd": { "metadata": { "exploitCode": "unknown", "remediation": "unknown", "reportConfidence": "confirmed", "type": "vulnerability" }, "osvSchema": { "aliases": [ "CVE-2021-47092" ], "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: VMX: Always clear vmx-\u003efail on emulation_required\n\nRevert a relatively recent change that set vmx-\u003efail if the vCPU is in L2\nand emulation_required is true, as that behavior is completely bogus.\nSetting vmx-\u003efail and synthesizing a VM-Exit is contradictory and wrong:\n\n (a) it\u0027s impossible to have both a VM-Fail and VM-Exit\n (b) vmcs.EXIT_REASON is not modified on VM-Fail\n (c) emulation_required refers to guest state and guest state checks are\n always VM-Exits, not VM-Fails.\n\nFor KVM specifically, emulation_required is handled before nested exits\nin __vmx_handle_exit(), thus setting vmx-\u003efail has no immediate effect,\ni.e. KVM calls into handle_invalid_guest_state() and vmx-\u003efail is ignored.\nSetting vmx-\u003efail can ultimately result in a WARN in nested_vmx_vmexit()\nfiring when tearing down the VM as KVM never expects vmx-\u003efail to be set\nwhen L2 is active, KVM always reflects those errors into L1.\n\n ------------[ cut here ]------------\n WARNING: CPU: 0 PID: 21158 at arch/x86/kvm/vmx/nested.c:4548\n nested_vmx_vmexit+0x16bd/0x17e0\n arch/x86/kvm/vmx/nested.c:4547\n Modules linked in:\n CPU: 0 PID: 21158 Comm: syz-executor.1 Not tainted 5.16.0-rc3-syzkaller #0\n Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011\n RIP: 0010:nested_vmx_vmexit+0x16bd/0x17e0 arch/x86/kvm/vmx/nested.c:4547\n Code: \u003c0f\u003e 0b e9 2e f8 ff ff e8 57 b3 5d 00 0f 0b e9 00 f1 ff ff 89 e9 80\n Call Trace:\n vmx_leave_nested arch/x86/kvm/vmx/nested.c:6220 [inline]\n nested_vmx_free_vcpu+0x83/0xc0 arch/x86/kvm/vmx/nested.c:330\n vmx_free_vcpu+0x11f/0x2a0 arch/x86/kvm/vmx/vmx.c:6799\n kvm_arch_vcpu_destroy+0x6b/0x240 arch/x86/kvm/x86.c:10989\n kvm_vcpu_destroy+0x29/0x90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:441\n kvm_free_vcpus arch/x86/kvm/x86.c:11426 [inline]\n kvm_arch_destroy_vm+0x3ef/0x6b0 arch/x86/kvm/x86.c:11545\n kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1189 [inline]\n kvm_put_kvm+0x751/0xe40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1220\n kvm_vcpu_release+0x53/0x60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3489\n __fput+0x3fc/0x870 fs/file_table.c:280\n task_work_run+0x146/0x1c0 kernel/task_work.c:164\n exit_task_work include/linux/task_work.h:32 [inline]\n do_exit+0x705/0x24f0 kernel/exit.c:832\n do_group_exit+0x168/0x2d0 kernel/exit.c:929\n get_signal+0x1740/0x2120 kernel/signal.c:2852\n arch_do_signal_or_restart+0x9c/0x730 arch/x86/kernel/signal.c:868\n handle_signal_work kernel/entry/common.c:148 [inline]\n exit_to_user_mode_loop kernel/entry/common.c:172 [inline]\n exit_to_user_mode_prepare+0x191/0x220 kernel/entry/common.c:207\n __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]\n syscall_exit_to_user_mode+0x2e/0x70 kernel/entry/common.c:300\n do_syscall_64+0x53/0xd0 arch/x86/entry/common.c:86\n entry_SYSCALL_64_after_hwframe+0x44/0xae", "id": "GSD-2021-47092", "modified": "2024-03-01T06:04:48.299103Z", "schema_version": "1.4.0" } }, "namespaces": { "cve.org": { "CVE_data_meta": { "ASSIGNER": "cve@kernel.org", "ID": "CVE-2021-47092", "STATE": "PUBLIC" }, "affects": { "vendor": { "vendor_data": [ { "product": { "product_data": [ { "product_name": "Linux", "version": { "version_data": [ { "version_affected": "\u003c", "version_name": "c8607e4a086f", "version_value": "e4e4e7cb2298" }, { "version_value": "not down converted", "x_cve_json_5_version_data": { "defaultStatus": "affected", "versions": [ { "status": "affected", "version": "5.15" }, { "lessThan": "5.15", "status": "unaffected", "version": "0", "versionType": "custom" }, { "lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.12", "versionType": "custom" }, { "lessThanOrEqual": "*", "status": "unaffected", "version": "5.16", "versionType": "original_commit_for_fix" } ] } } ] } } ] }, "vendor_name": "Linux" } ] } }, "data_format": "MITRE", "data_type": "CVE", "data_version": "4.0", "description": { "description_data": [ { "lang": "eng", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: VMX: Always clear vmx-\u003efail on emulation_required\n\nRevert a relatively recent change that set vmx-\u003efail if the vCPU is in L2\nand emulation_required is true, as that behavior is completely bogus.\nSetting vmx-\u003efail and synthesizing a VM-Exit is contradictory and wrong:\n\n (a) it\u0027s impossible to have both a VM-Fail and VM-Exit\n (b) vmcs.EXIT_REASON is not modified on VM-Fail\n (c) emulation_required refers to guest state and guest state checks are\n always VM-Exits, not VM-Fails.\n\nFor KVM specifically, emulation_required is handled before nested exits\nin __vmx_handle_exit(), thus setting vmx-\u003efail has no immediate effect,\ni.e. KVM calls into handle_invalid_guest_state() and vmx-\u003efail is ignored.\nSetting vmx-\u003efail can ultimately result in a WARN in nested_vmx_vmexit()\nfiring when tearing down the VM as KVM never expects vmx-\u003efail to be set\nwhen L2 is active, KVM always reflects those errors into L1.\n\n ------------[ cut here ]------------\n WARNING: CPU: 0 PID: 21158 at arch/x86/kvm/vmx/nested.c:4548\n nested_vmx_vmexit+0x16bd/0x17e0\n arch/x86/kvm/vmx/nested.c:4547\n Modules linked in:\n CPU: 0 PID: 21158 Comm: syz-executor.1 Not tainted 5.16.0-rc3-syzkaller #0\n Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011\n RIP: 0010:nested_vmx_vmexit+0x16bd/0x17e0 arch/x86/kvm/vmx/nested.c:4547\n Code: \u003c0f\u003e 0b e9 2e f8 ff ff e8 57 b3 5d 00 0f 0b e9 00 f1 ff ff 89 e9 80\n Call Trace:\n vmx_leave_nested arch/x86/kvm/vmx/nested.c:6220 [inline]\n nested_vmx_free_vcpu+0x83/0xc0 arch/x86/kvm/vmx/nested.c:330\n vmx_free_vcpu+0x11f/0x2a0 arch/x86/kvm/vmx/vmx.c:6799\n kvm_arch_vcpu_destroy+0x6b/0x240 arch/x86/kvm/x86.c:10989\n kvm_vcpu_destroy+0x29/0x90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:441\n kvm_free_vcpus arch/x86/kvm/x86.c:11426 [inline]\n kvm_arch_destroy_vm+0x3ef/0x6b0 arch/x86/kvm/x86.c:11545\n kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1189 [inline]\n kvm_put_kvm+0x751/0xe40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1220\n kvm_vcpu_release+0x53/0x60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3489\n __fput+0x3fc/0x870 fs/file_table.c:280\n task_work_run+0x146/0x1c0 kernel/task_work.c:164\n exit_task_work include/linux/task_work.h:32 [inline]\n do_exit+0x705/0x24f0 kernel/exit.c:832\n do_group_exit+0x168/0x2d0 kernel/exit.c:929\n get_signal+0x1740/0x2120 kernel/signal.c:2852\n arch_do_signal_or_restart+0x9c/0x730 arch/x86/kernel/signal.c:868\n handle_signal_work kernel/entry/common.c:148 [inline]\n exit_to_user_mode_loop kernel/entry/common.c:172 [inline]\n exit_to_user_mode_prepare+0x191/0x220 kernel/entry/common.c:207\n __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]\n syscall_exit_to_user_mode+0x2e/0x70 kernel/entry/common.c:300\n do_syscall_64+0x53/0xd0 arch/x86/entry/common.c:86\n entry_SYSCALL_64_after_hwframe+0x44/0xae" } ] }, "generator": { "engine": "bippy-4986f5686161" }, "problemtype": { "problemtype_data": [ { "description": [ { "lang": "eng", "value": "n/a" } ] } ] }, "references": { "reference_data": [ { "name": "https://git.kernel.org/stable/c/e4e4e7cb229821cd215031abc47efdab5486a67c", "refsource": "MISC", "url": "https://git.kernel.org/stable/c/e4e4e7cb229821cd215031abc47efdab5486a67c" }, { "name": "https://git.kernel.org/stable/c/a80dfc025924024d2c61a4c1b8ef62b2fce76a04", "refsource": "MISC", "url": "https://git.kernel.org/stable/c/a80dfc025924024d2c61a4c1b8ef62b2fce76a04" } ] } }, "nvd.nist.gov": { "cve": { "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: VMX: Always clear vmx-\u003efail on emulation_required\n\nRevert a relatively recent change that set vmx-\u003efail if the vCPU is in L2\nand emulation_required is true, as that behavior is completely bogus.\nSetting vmx-\u003efail and synthesizing a VM-Exit is contradictory and wrong:\n\n (a) it\u0027s impossible to have both a VM-Fail and VM-Exit\n (b) vmcs.EXIT_REASON is not modified on VM-Fail\n (c) emulation_required refers to guest state and guest state checks are\n always VM-Exits, not VM-Fails.\n\nFor KVM specifically, emulation_required is handled before nested exits\nin __vmx_handle_exit(), thus setting vmx-\u003efail has no immediate effect,\ni.e. KVM calls into handle_invalid_guest_state() and vmx-\u003efail is ignored.\nSetting vmx-\u003efail can ultimately result in a WARN in nested_vmx_vmexit()\nfiring when tearing down the VM as KVM never expects vmx-\u003efail to be set\nwhen L2 is active, KVM always reflects those errors into L1.\n\n ------------[ cut here ]------------\n WARNING: CPU: 0 PID: 21158 at arch/x86/kvm/vmx/nested.c:4548\n nested_vmx_vmexit+0x16bd/0x17e0\n arch/x86/kvm/vmx/nested.c:4547\n Modules linked in:\n CPU: 0 PID: 21158 Comm: syz-executor.1 Not tainted 5.16.0-rc3-syzkaller #0\n Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011\n RIP: 0010:nested_vmx_vmexit+0x16bd/0x17e0 arch/x86/kvm/vmx/nested.c:4547\n Code: \u003c0f\u003e 0b e9 2e f8 ff ff e8 57 b3 5d 00 0f 0b e9 00 f1 ff ff 89 e9 80\n Call Trace:\n vmx_leave_nested arch/x86/kvm/vmx/nested.c:6220 [inline]\n nested_vmx_free_vcpu+0x83/0xc0 arch/x86/kvm/vmx/nested.c:330\n vmx_free_vcpu+0x11f/0x2a0 arch/x86/kvm/vmx/vmx.c:6799\n kvm_arch_vcpu_destroy+0x6b/0x240 arch/x86/kvm/x86.c:10989\n kvm_vcpu_destroy+0x29/0x90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:441\n kvm_free_vcpus arch/x86/kvm/x86.c:11426 [inline]\n kvm_arch_destroy_vm+0x3ef/0x6b0 arch/x86/kvm/x86.c:11545\n kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1189 [inline]\n kvm_put_kvm+0x751/0xe40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1220\n kvm_vcpu_release+0x53/0x60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3489\n __fput+0x3fc/0x870 fs/file_table.c:280\n task_work_run+0x146/0x1c0 kernel/task_work.c:164\n exit_task_work include/linux/task_work.h:32 [inline]\n do_exit+0x705/0x24f0 kernel/exit.c:832\n do_group_exit+0x168/0x2d0 kernel/exit.c:929\n get_signal+0x1740/0x2120 kernel/signal.c:2852\n arch_do_signal_or_restart+0x9c/0x730 arch/x86/kernel/signal.c:868\n handle_signal_work kernel/entry/common.c:148 [inline]\n exit_to_user_mode_loop kernel/entry/common.c:172 [inline]\n exit_to_user_mode_prepare+0x191/0x220 kernel/entry/common.c:207\n __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]\n syscall_exit_to_user_mode+0x2e/0x70 kernel/entry/common.c:300\n do_syscall_64+0x53/0xd0 arch/x86/entry/common.c:86\n entry_SYSCALL_64_after_hwframe+0x44/0xae" } ], "id": "CVE-2021-47092", "lastModified": "2024-03-05T13:41:01.900", "metrics": {}, "published": "2024-03-04T18:15:07.723", "references": [ { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/a80dfc025924024d2c61a4c1b8ef62b2fce76a04" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/e4e4e7cb229821cd215031abc47efdab5486a67c" } ], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Awaiting Analysis" } } } }
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- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
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