kernel.git/arch/x86/kernel/cpu, branch linux-5.6.y

x86/{mce,mm}: Unmap the entire page if the whole page is affected and poisoned

2020-06-17T14:42:01Z

commit 17fae1294ad9d711b2c3dd0edef479d40c76a5e8 upstream. An interesting thing happened when a guest Linux instance took a machine check. The VMM unmapped the bad page from guest physical space and passed the machine check to the guest. Linux took all the normal actions to offline the page from the process that was using it. But then guest Linux crashed because it said there was a second machine check inside the kernel with this stack trace: do_memory_failure set_mce_nospec set_memory_uc _set_memory_uc change_page_attr_set_clr cpa_flush clflush_cache_range_opt This was odd, because a CLFLUSH instruction shouldn't raise a machine check (it isn't consuming the data). Further investigation showed that the VMM had passed in another machine check because is appeared that the guest was accessing the bad page. Fix is to check the scope of the poison by checking the MCi_MISC register. If the entire page is affected, then unmap the page. If only part of the page is affected, then mark the page as uncacheable. This assumes that VMMs will do the logical thing and pass in the "whole page scope" via the MCi_MISC register (since they unmapped the entire page). [ bp: Adjust to x86/entry changes. ] Fixes: 284ce4011ba6 ("x86/memory_failure: Introduce {set, clear}_mce_nospec()") Reported-by: Jue Wang Signed-off-by: Tony Luck Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Jue Wang Cc: Link: https://lkml.kernel.org/r/20200520163546.GA7977@agluck-desk2.amr.corp.intel.com Signed-off-by: Greg Kroah-Hartman

x86/speculation: PR_SPEC_FORCE_DISABLE enforcement for indirect branches.

2020-06-17T14:41:54Z

commit 4d8df8cbb9156b0a0ab3f802b80cb5db57acc0bf upstream. Currently, it is possible to enable indirect branch speculation even after it was force-disabled using the PR_SPEC_FORCE_DISABLE option. Moreover, the PR_GET_SPECULATION_CTRL command gives afterwards an incorrect result (force-disabled when it is in fact enabled). This also is inconsistent vs. STIBP and the documention which cleary states that PR_SPEC_FORCE_DISABLE cannot be undone. Fix this by actually enforcing force-disabled indirect branch speculation. PR_SPEC_ENABLE called after PR_SPEC_FORCE_DISABLE now fails with -EPERM as described in the documentation. Fixes: 9137bb27e60e ("x86/speculation: Add prctl() control for indirect branch speculation") Signed-off-by: Anthony Steinhauser Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman

x86/speculation: Avoid force-disabling IBPB based on STIBP and enhanced IBRS.

2020-06-17T14:41:54Z

commit 21998a351512eba4ed5969006f0c55882d995ada upstream. When STIBP is unavailable or enhanced IBRS is available, Linux force-disables the IBPB mitigation of Spectre-BTB even when simultaneous multithreading is disabled. While attempts to enable IBPB using prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, ...) fail with EPERM, the seccomp syscall (or its prctl(PR_SET_SECCOMP, ...) equivalent) which are used e.g. by Chromium or OpenSSH succeed with no errors but the application remains silently vulnerable to cross-process Spectre v2 attacks (classical BTB poisoning). At the same time the SYSFS reporting (/sys/devices/system/cpu/vulnerabilities/spectre_v2) displays that IBPB is conditionally enabled when in fact it is unconditionally disabled. STIBP is useful only when SMT is enabled. When SMT is disabled and STIBP is unavailable, it makes no sense to force-disable also IBPB, because IBPB protects against cross-process Spectre-BTB attacks regardless of the SMT state. At the same time since missing STIBP was only observed on AMD CPUs, AMD does not recommend using STIBP, but recommends using IBPB, so disabling IBPB because of missing STIBP goes directly against AMD's advice: https://developer.amd.com/wp-content/resources/Architecture_Guidelines_Update_Indirect_Branch_Control.pdf Similarly, enhanced IBRS is designed to protect cross-core BTB poisoning and BTB-poisoning attacks from user space against kernel (and BTB-poisoning attacks from guest against hypervisor), it is not designed to prevent cross-process (or cross-VM) BTB poisoning between processes (or VMs) running on the same core. Therefore, even with enhanced IBRS it is necessary to flush the BTB during context-switches, so there is no reason to force disable IBPB when enhanced IBRS is available. Enable the prctl control of IBPB even when STIBP is unavailable or enhanced IBRS is available. Fixes: 7cc765a67d8e ("x86/speculation: Enable prctl mode for spectre_v2_user") Signed-off-by: Anthony Steinhauser Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman

x86/cpu/amd: Make erratum #1054 a legacy erratum

2020-06-17T14:41:52Z

[ Upstream commit e2abfc0448a46d8a137505aa180caf14070ec535 ] Commit 21b5ee59ef18 ("x86/cpu/amd: Enable the fixed Instructions Retired counter IRPERF") mistakenly added erratum #1054 as an OS Visible Workaround (OSVW) ID 0. Erratum #1054 is not OSVW ID 0 [1], so make it a legacy erratum. There would never have been a false positive on older hardware that has OSVW bit 0 set, since the IRPERF feature was not available. However, save a couple of RDMSR executions per thread, on modern system configurations that correctly set non-zero values in their OSVW_ID_Length MSRs. [1] Revision Guide for AMD Family 17h Models 00h-0Fh Processors. The revision guide is available from the bugzilla link below. Fixes: 21b5ee59ef18 ("x86/cpu/amd: Enable the fixed Instructions Retired counter IRPERF") Reported-by: Andrew Cooper Signed-off-by: Kim Phillips Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20200417143356.26054-1-kim.phillips@amd.com Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 Signed-off-by: Sasha Levin

x86/speculation: Add Special Register Buffer Data Sampling (SRBDS) mitigation

2020-06-10T18:22:52Z

commit 7e5b3c267d256822407a22fdce6afdf9cd13f9fb upstream SRBDS is an MDS-like speculative side channel that can leak bits from the random number generator (RNG) across cores and threads. New microcode serializes the processor access during the execution of RDRAND and RDSEED. This ensures that the shared buffer is overwritten before it is released for reuse. While it is present on all affected CPU models, the microcode mitigation is not needed on models that enumerate ARCH_CAPABILITIES[MDS_NO] in the cases where TSX is not supported or has been disabled with TSX_CTRL. The mitigation is activated by default on affected processors and it increases latency for RDRAND and RDSEED instructions. Among other effects this will reduce throughput from /dev/urandom. * Enable administrator to configure the mitigation off when desired using either mitigations=off or srbds=off. * Export vulnerability status via sysfs * Rename file-scoped macros to apply for non-whitelist table initializations. [ bp: Massage, - s/VULNBL_INTEL_STEPPING/VULNBL_INTEL_STEPPINGS/g, - do not read arch cap MSR a second time in tsx_fused_off() - just pass it in, - flip check in cpu_set_bug_bits() to save an indentation level, - reflow comments. jpoimboe: s/Mitigated/Mitigation/ in user-visible strings tglx: Dropped the fused off magic for now ] Signed-off-by: Mark Gross Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Reviewed-by: Tony Luck Reviewed-by: Pawan Gupta Reviewed-by: Josh Poimboeuf Tested-by: Neelima Krishnan Signed-off-by: Greg Kroah-Hartman

x86/cpu: Add 'table' argument to cpu_matches()

2020-06-10T18:22:52Z

commit 93920f61c2ad7edb01e63323832585796af75fc9 upstream To make cpu_matches() reusable for other matching tables, have it take a pointer to a x86_cpu_id table as an argument. [ bp: Flip arguments order. ] Signed-off-by: Mark Gross Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Reviewed-by: Josh Poimboeuf Signed-off-by: Greg Kroah-Hartman

x86/cpu: Add a steppings field to struct x86_cpu_id

2020-06-10T18:22:52Z

commit e9d7144597b10ff13ff2264c059f7d4a7fbc89ac upstream Intel uses the same family/model for several CPUs. Sometimes the stepping must be checked to tell them apart. On x86 there can be at most 16 steppings. Add a steppings bitmask to x86_cpu_id and a X86_MATCH_VENDOR_FAMILY_MODEL_STEPPING_FEATURE macro and support for matching against family/model/stepping. [ bp: Massage. tglx: Lightweight variant for backporting ] Signed-off-by: Mark Gross Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Reviewed-by: Tony Luck Reviewed-by: Josh Poimboeuf Signed-off-by: Greg Kroah-Hartman

x86: hyperv: report value of misc_features

2020-05-02T06:50:57Z

[ Upstream commit 97d9f1c43bedd400301d6f1eff54d46e8c636e47 ] A few kernel features depend on ms_hyperv.misc_features, but unlike its siblings ->features and ->hints, the value was never reported during boot. Signed-off-by: Olaf Hering Link: https://lore.kernel.org/r/20200407172739.31371-1-olaf@aepfle.de Signed-off-by: Wei Liu Signed-off-by: Sasha Levin

x86/Hyper-V: Report crash register data or kmsg before running crash kernel

2020-04-23T08:37:55Z

commit a11589563e96bf262767294b89b25a9d44e7303b upstream. We want to notify Hyper-V when a Linux guest VM crash occurs, so there is a record of the crash even when kdump is enabled. But crash_kexec_post_notifiers defaults to "false", so the kdump kernel runs before the notifiers and Hyper-V never gets notified. Fix this by always setting crash_kexec_post_notifiers to be true for Hyper-V VMs. Fixes: 81b18bce48af ("Drivers: HV: Send one page worth of kmsg dump over Hyper-V during panic") Reviewed-by: Michael Kelley Signed-off-by: Tianyu Lan Link: https://lore.kernel.org/r/20200406155331.2105-5-Tianyu.Lan@microsoft.com Signed-off-by: Wei Liu Signed-off-by: Greg Kroah-Hartman

x86/resctrl: Fix invalid attempt at removing the default resource group

2020-04-21T07:08:16Z

commit b0151da52a6d4f3951ea24c083e7a95977621436 upstream. The default resource group ("rdtgroup_default") is associated with the root of the resctrl filesystem and should never be removed. New resource groups can be created as subdirectories of the resctrl filesystem and they can be removed from user space. There exists a safeguard in the directory removal code (rdtgroup_rmdir()) that ensures that only subdirectories can be removed by testing that the directory to be removed has to be a child of the root directory. A possible deadlock was recently fixed with 334b0f4e9b1b ("x86/resctrl: Fix a deadlock due to inaccurate reference"). This fix involved associating the private data of the "mon_groups" and "mon_data" directories to the resource group to which they belong instead of NULL as before. A consequence of this change was that the original safeguard code preventing removal of "mon_groups" and "mon_data" found in the root directory failed resulting in attempts to remove the default resource group that ends in a BUG: kernel BUG at mm/slub.c:3969! invalid opcode: 0000 [#1] SMP PTI Call Trace: rdtgroup_rmdir+0x16b/0x2c0 kernfs_iop_rmdir+0x5c/0x90 vfs_rmdir+0x7a/0x160 do_rmdir+0x17d/0x1e0 do_syscall_64+0x55/0x1d0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fix this by improving the directory removal safeguard to ensure that subdirectories of the resctrl root directory can only be removed if they are a child of the resctrl filesystem's root _and_ not associated with the default resource group. Fixes: 334b0f4e9b1b ("x86/resctrl: Fix a deadlock due to inaccurate reference") Reported-by: Sai Praneeth Prakhya Signed-off-by: Reinette Chatre Signed-off-by: Borislav Petkov Tested-by: Sai Praneeth Prakhya Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/884cbe1773496b5dbec1b6bd11bb50cffa83603d.1584461853.git.reinette.chatre@intel.com Signed-off-by: Greg Kroah-Hartman