diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-devices-system-cpu | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/hw-vuln/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/hw-vuln/vmscape.rst | 110 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 11 | ||||
| -rw-r--r-- | Documentation/netlink/specs/mptcp_pm.yaml | 2 | ||||
| -rw-r--r-- | Documentation/networking/can.rst | 2 | ||||
| -rw-r--r-- | Documentation/networking/mptcp.rst | 8 |
7 files changed, 129 insertions, 6 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index ab8cd337f43a..8aed6d94c4cd 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -586,6 +586,7 @@ What: /sys/devices/system/cpu/vulnerabilities /sys/devices/system/cpu/vulnerabilities/srbds /sys/devices/system/cpu/vulnerabilities/tsa /sys/devices/system/cpu/vulnerabilities/tsx_async_abort + /sys/devices/system/cpu/vulnerabilities/vmscape Date: January 2018 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> Description: Information about CPU vulnerabilities diff --git a/Documentation/admin-guide/hw-vuln/index.rst b/Documentation/admin-guide/hw-vuln/index.rst index 89ca636081b7..55d747511f83 100644 --- a/Documentation/admin-guide/hw-vuln/index.rst +++ b/Documentation/admin-guide/hw-vuln/index.rst @@ -26,3 +26,4 @@ are configurable at compile, boot or run time. rsb old_microcode indirect-target-selection + vmscape diff --git a/Documentation/admin-guide/hw-vuln/vmscape.rst b/Documentation/admin-guide/hw-vuln/vmscape.rst new file mode 100644 index 000000000000..d9b9a2b6c114 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/vmscape.rst @@ -0,0 +1,110 @@ +.. SPDX-License-Identifier: GPL-2.0 + +VMSCAPE +======= + +VMSCAPE is a vulnerability that may allow a guest to influence the branch +prediction in host userspace. It particularly affects hypervisors like QEMU. + +Even if a hypervisor may not have any sensitive data like disk encryption keys, +guest-userspace may be able to attack the guest-kernel using the hypervisor as +a confused deputy. + +Affected processors +------------------- + +The following CPU families are affected by VMSCAPE: + +**Intel processors:** + - Skylake generation (Parts without Enhanced-IBRS) + - Cascade Lake generation - (Parts affected by ITS guest/host separation) + - Alder Lake and newer (Parts affected by BHI) + +Note that, BHI affected parts that use BHB clearing software mitigation e.g. +Icelake are not vulnerable to VMSCAPE. + +**AMD processors:** + - Zen series (families 0x17, 0x19, 0x1a) + +** Hygon processors:** + - Family 0x18 + +Mitigation +---------- + +Conditional IBPB +---------------- + +Kernel tracks when a CPU has run a potentially malicious guest and issues an +IBPB before the first exit to userspace after VM-exit. If userspace did not run +between VM-exit and the next VM-entry, no IBPB is issued. + +Note that the existing userspace mitigation against Spectre-v2 is effective in +protecting the userspace. They are insufficient to protect the userspace VMMs +from a malicious guest. This is because Spectre-v2 mitigations are applied at +context switch time, while the userspace VMM can run after a VM-exit without a +context switch. + +Vulnerability enumeration and mitigation is not applied inside a guest. This is +because nested hypervisors should already be deploying IBPB to isolate +themselves from nested guests. + +SMT considerations +------------------ + +When Simultaneous Multi-Threading (SMT) is enabled, hypervisors can be +vulnerable to cross-thread attacks. For complete protection against VMSCAPE +attacks in SMT environments, STIBP should be enabled. + +The kernel will issue a warning if SMT is enabled without adequate STIBP +protection. Warning is not issued when: + +- SMT is disabled +- STIBP is enabled system-wide +- Intel eIBRS is enabled (which implies STIBP protection) + +System information and options +------------------------------ + +The sysfs file showing VMSCAPE mitigation status is: + + /sys/devices/system/cpu/vulnerabilities/vmscape + +The possible values in this file are: + + * 'Not affected': + + The processor is not vulnerable to VMSCAPE attacks. + + * 'Vulnerable': + + The processor is vulnerable and no mitigation has been applied. + + * 'Mitigation: IBPB before exit to userspace': + + Conditional IBPB mitigation is enabled. The kernel tracks when a CPU has + run a potentially malicious guest and issues an IBPB before the first + exit to userspace after VM-exit. + + * 'Mitigation: IBPB on VMEXIT': + + IBPB is issued on every VM-exit. This occurs when other mitigations like + RETBLEED or SRSO are already issuing IBPB on VM-exit. + +Mitigation control on the kernel command line +---------------------------------------------- + +The mitigation can be controlled via the ``vmscape=`` command line parameter: + + * ``vmscape=off``: + + Disable the VMSCAPE mitigation. + + * ``vmscape=ibpb``: + + Enable conditional IBPB mitigation (default when CONFIG_MITIGATION_VMSCAPE=y). + + * ``vmscape=force``: + + Force vulnerability detection and mitigation even on processors that are + not known to be affected. diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 747a55abf494..5a7a83c411e9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3829,6 +3829,7 @@ srbds=off [X86,INTEL] ssbd=force-off [ARM64] tsx_async_abort=off [X86] + vmscape=off [X86] Exceptions: This does not have any effect on @@ -8041,6 +8042,16 @@ vmpoff= [KNL,S390] Perform z/VM CP command after power off. Format: <command> + vmscape= [X86] Controls mitigation for VMscape attacks. + VMscape attacks can leak information from a userspace + hypervisor to a guest via speculative side-channels. + + off - disable the mitigation + ibpb - use Indirect Branch Prediction Barrier + (IBPB) mitigation (default) + force - force vulnerability detection even on + unaffected processors + vsyscall= [X86-64,EARLY] Controls the behavior of vsyscalls (i.e. calls to fixed addresses of 0xffffffffff600x00 from legacy diff --git a/Documentation/netlink/specs/mptcp_pm.yaml b/Documentation/netlink/specs/mptcp_pm.yaml index 02f1ddcfbf1c..d15335684ec3 100644 --- a/Documentation/netlink/specs/mptcp_pm.yaml +++ b/Documentation/netlink/specs/mptcp_pm.yaml @@ -256,7 +256,7 @@ attribute-sets: type: u32 - name: if-idx - type: u32 + type: s32 - name: reset-reason type: u32 diff --git a/Documentation/networking/can.rst b/Documentation/networking/can.rst index bc1b585355f7..7650c4b5be5f 100644 --- a/Documentation/networking/can.rst +++ b/Documentation/networking/can.rst @@ -742,7 +742,7 @@ The broadcast manager sends responses to user space in the same form: struct timeval ival1, ival2; /* count and subsequent interval */ canid_t can_id; /* unique can_id for task */ __u32 nframes; /* number of can_frames following */ - struct can_frame frames[0]; + struct can_frame frames[]; }; The aligned payload 'frames' uses the same basic CAN frame structure defined diff --git a/Documentation/networking/mptcp.rst b/Documentation/networking/mptcp.rst index 17f2bab61164..2e31038d6462 100644 --- a/Documentation/networking/mptcp.rst +++ b/Documentation/networking/mptcp.rst @@ -60,10 +60,10 @@ address announcements. Typically, it is the client side that initiates subflows, and the server side that announces additional addresses via the ``ADD_ADDR`` and ``REMOVE_ADDR`` options. -Path managers are controlled by the ``net.mptcp.pm_type`` sysctl knob -- see -mptcp-sysctl.rst. There are two types: the in-kernel one (type ``0``) where the -same rules are applied for all the connections (see: ``ip mptcp``) ; and the -userspace one (type ``1``), controlled by a userspace daemon (i.e. `mptcpd +Path managers are controlled by the ``net.mptcp.path_manager`` sysctl knob -- +see mptcp-sysctl.rst. There are two types: the in-kernel one (``kernel``) where +the same rules are applied for all the connections (see: ``ip mptcp``) ; and the +userspace one (``userspace``), controlled by a userspace daemon (i.e. `mptcpd <https://mptcpd.mptcp.dev/>`_) where different rules can be applied for each connection. The path managers can be controlled via a Netlink API; see netlink_spec/mptcp_pm.rst. |