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2024-04-25x86/bugs: Switch to new Intel CPU model definesTony Luck
New CPU #defines encode vendor and family as well as model. Signed-off-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Link: https://lore.kernel.org/r/20240424181506.41673-1-tony.luck@intel.com
2024-04-14x86/bugs: Fix BHI retpoline checkJosh Poimboeuf
Confusingly, X86_FEATURE_RETPOLINE doesn't mean retpolines are enabled, as it also includes the original "AMD retpoline" which isn't a retpoline at all. Also replace cpu_feature_enabled() with boot_cpu_has() because this is before alternatives are patched and cpu_feature_enabled()'s fallback path is slower than plain old boot_cpu_has(). Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/ad3807424a3953f0323c011a643405619f2a4927.1712944776.git.jpoimboe@kernel.org
2024-04-12x86/bugs: Replace CONFIG_SPECTRE_BHI_{ON,OFF} with CONFIG_MITIGATION_SPECTRE_BHIJosh Poimboeuf
For consistency with the other CONFIG_MITIGATION_* options, replace the CONFIG_SPECTRE_BHI_{ON,OFF} options with a single CONFIG_MITIGATION_SPECTRE_BHI option. [ mingo: Fix ] Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Sean Christopherson <seanjc@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nikolay Borisov <nik.borisov@suse.com> Link: https://lore.kernel.org/r/3833812ea63e7fdbe36bf8b932e63f70d18e2a2a.1712813475.git.jpoimboe@kernel.org
2024-04-12x86/bugs: Remove CONFIG_BHI_MITIGATION_AUTO and spectre_bhi=autoJosh Poimboeuf
Unlike most other mitigations' "auto" options, spectre_bhi=auto only mitigates newer systems, which is confusing and not particularly useful. Remove it. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Nikolay Borisov <nik.borisov@suse.com> Cc: Sean Christopherson <seanjc@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/412e9dc87971b622bbbaf64740ebc1f140bff343.1712813475.git.jpoimboe@kernel.org
2024-04-11x86/bugs: Clarify that syscall hardening isn't a BHI mitigationJosh Poimboeuf
While syscall hardening helps prevent some BHI attacks, there's still other low-hanging fruit remaining. Don't classify it as a mitigation and make it clear that the system may still be vulnerable if it doesn't have a HW or SW mitigation enabled. Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Sean Christopherson <seanjc@google.com> Link: https://lore.kernel.org/r/b5951dae3fdee7f1520d5136a27be3bdfe95f88b.1712813475.git.jpoimboe@kernel.org
2024-04-11x86/bugs: Fix BHI handling of RRSBAJosh Poimboeuf
The ARCH_CAP_RRSBA check isn't correct: RRSBA may have already been disabled by the Spectre v2 mitigation (or can otherwise be disabled by the BHI mitigation itself if needed). In that case retpolines are fine. Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Sean Christopherson <seanjc@google.com> Link: https://lore.kernel.org/r/6f56f13da34a0834b69163467449be7f58f253dc.1712813475.git.jpoimboe@kernel.org
2024-04-11x86/bugs: Rename various 'ia32_cap' variables to 'x86_arch_cap_msr'Ingo Molnar
So we are using the 'ia32_cap' value in a number of places, which got its name from MSR_IA32_ARCH_CAPABILITIES MSR register. But there's very little 'IA32' about it - this isn't 32-bit only code, nor does it originate from there, it's just a historic quirk that many Intel MSR names are prefixed with IA32_. This is already clear from the helper method around the MSR: x86_read_arch_cap_msr(), which doesn't have the IA32 prefix. So rename 'ia32_cap' to 'x86_arch_cap_msr' to be consistent with its role and with the naming of the helper function. Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Nikolay Borisov <nik.borisov@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Sean Christopherson <seanjc@google.com> Link: https://lore.kernel.org/r/9592a18a814368e75f8f4b9d74d3883aa4fd1eaf.1712813475.git.jpoimboe@kernel.org
2024-04-11x86/bugs: Cache the value of MSR_IA32_ARCH_CAPABILITIESJosh Poimboeuf
There's no need to keep reading MSR_IA32_ARCH_CAPABILITIES over and over. It's even read in the BHI sysfs function which is a big no-no. Just read it once and cache it. Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Nikolay Borisov <nik.borisov@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Sean Christopherson <seanjc@google.com> Link: https://lore.kernel.org/r/9592a18a814368e75f8f4b9d74d3883aa4fd1eaf.1712813475.git.jpoimboe@kernel.org
2024-04-10x86/bugs: Fix return type of spectre_bhi_state()Daniel Sneddon
The definition of spectre_bhi_state() incorrectly returns a const char * const. This causes the a compiler warning when building with W=1: warning: type qualifiers ignored on function return type [-Wignored-qualifiers] 2812 | static const char * const spectre_bhi_state(void) Remove the const qualifier from the pointer. Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") Reported-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20240409230806.1545822-1-daniel.sneddon@linux.intel.com
2024-04-08x86/bhi: Mitigate KVM by defaultPawan Gupta
BHI mitigation mode spectre_bhi=auto does not deploy the software mitigation by default. In a cloud environment, it is a likely scenario where userspace is trusted but the guests are not trusted. Deploying system wide mitigation in such cases is not desirable. Update the auto mode to unconditionally mitigate against malicious guests. Deploy the software sequence at VMexit in auto mode also, when hardware mitigation is not available. Unlike the force =on mode, software sequence is not deployed at syscalls in auto mode. Suggested-by: Alexandre Chartre <alexandre.chartre@oracle.com> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
2024-04-08x86/bhi: Add BHI mitigation knobPawan Gupta
Branch history clearing software sequences and hardware control BHI_DIS_S were defined to mitigate Branch History Injection (BHI). Add cmdline spectre_bhi={on|off|auto} to control BHI mitigation: auto - Deploy the hardware mitigation BHI_DIS_S, if available. on - Deploy the hardware mitigation BHI_DIS_S, if available, otherwise deploy the software sequence at syscall entry and VMexit. off - Turn off BHI mitigation. The default is auto mode which does not deploy the software sequence mitigation. This is because of the hardening done in the syscall dispatch path, which is the likely target of BHI. Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
2024-04-08x86/bugs: Change commas to semicolons in 'spectre_v2' sysfs fileJosh Poimboeuf
Change the format of the 'spectre_v2' vulnerabilities sysfs file slightly by converting the commas to semicolons, so that mitigations for future variants can be grouped together and separated by commas. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2024-03-12Merge tag 'rfds-for-linus-2024-03-11' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86 RFDS mitigation from Dave Hansen: "RFDS is a CPU vulnerability that may allow a malicious userspace to infer stale register values from kernel space. Kernel registers can have all kinds of secrets in them so the mitigation is basically to wait until the kernel is about to return to userspace and has user values in the registers. At that point there is little chance of kernel secrets ending up in the registers and the microarchitectural state can be cleared. This leverages some recent robustness fixes for the existing MDS vulnerability. Both MDS and RFDS use the VERW instruction for mitigation" * tag 'rfds-for-linus-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: KVM/x86: Export RFDS_NO and RFDS_CLEAR to guests x86/rfds: Mitigate Register File Data Sampling (RFDS) Documentation/hw-vuln: Add documentation for RFDS x86/mmio: Disable KVM mitigation when X86_FEATURE_CLEAR_CPU_BUF is set
2024-03-11Merge tag 'x86-core-2024-03-11' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull core x86 updates from Ingo Molnar: - The biggest change is the rework of the percpu code, to support the 'Named Address Spaces' GCC feature, by Uros Bizjak: - This allows C code to access GS and FS segment relative memory via variables declared with such attributes, which allows the compiler to better optimize those accesses than the previous inline assembly code. - The series also includes a number of micro-optimizations for various percpu access methods, plus a number of cleanups of %gs accesses in assembly code. - These changes have been exposed to linux-next testing for the last ~5 months, with no known regressions in this area. - Fix/clean up __switch_to()'s broken but accidentally working handling of FPU switching - which also generates better code - Propagate more RIP-relative addressing in assembly code, to generate slightly better code - Rework the CPU mitigations Kconfig space to be less idiosyncratic, to make it easier for distros to follow & maintain these options - Rework the x86 idle code to cure RCU violations and to clean up the logic - Clean up the vDSO Makefile logic - Misc cleanups and fixes * tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits) x86/idle: Select idle routine only once x86/idle: Let prefer_mwait_c1_over_halt() return bool x86/idle: Cleanup idle_setup() x86/idle: Clean up idle selection x86/idle: Sanitize X86_BUG_AMD_E400 handling sched/idle: Conditionally handle tick broadcast in default_idle_call() x86: Increase brk randomness entropy for 64-bit systems x86/vdso: Move vDSO to mmap region x86/vdso/kbuild: Group non-standard build attributes and primary object file rules together x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o x86/retpoline: Ensure default return thunk isn't used at runtime x86/vdso: Use CONFIG_COMPAT_32 to specify vdso32 x86/vdso: Use $(addprefix ) instead of $(foreach ) x86/vdso: Simplify obj-y addition x86/vdso: Consolidate targets and clean-files x86/bugs: Rename CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK x86/bugs: Rename CONFIG_CPU_SRSO => CONFIG_MITIGATION_SRSO x86/bugs: Rename CONFIG_CPU_IBRS_ENTRY => CONFIG_MITIGATION_IBRS_ENTRY x86/bugs: Rename CONFIG_CPU_UNRET_ENTRY => CONFIG_MITIGATION_UNRET_ENTRY x86/bugs: Rename CONFIG_SLS => CONFIG_MITIGATION_SLS ...
2024-03-11x86/rfds: Mitigate Register File Data Sampling (RFDS)Pawan Gupta
RFDS is a CPU vulnerability that may allow userspace to infer kernel stale data previously used in floating point registers, vector registers and integer registers. RFDS only affects certain Intel Atom processors. Intel released a microcode update that uses VERW instruction to clear the affected CPU buffers. Unlike MDS, none of the affected cores support SMT. Add RFDS bug infrastructure and enable the VERW based mitigation by default, that clears the affected buffers just before exiting to userspace. Also add sysfs reporting and cmdline parameter "reg_file_data_sampling" to control the mitigation. For details see: Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
2024-03-11x86/mmio: Disable KVM mitigation when X86_FEATURE_CLEAR_CPU_BUF is setPawan Gupta
Currently MMIO Stale Data mitigation for CPUs not affected by MDS/TAA is to only deploy VERW at VMentry by enabling mmio_stale_data_clear static branch. No mitigation is needed for kernel->user transitions. If such CPUs are also affected by RFDS, its mitigation may set X86_FEATURE_CLEAR_CPU_BUF to deploy VERW at kernel->user and VMentry. This could result in duplicate VERW at VMentry. Fix this by disabling mmio_stale_data_clear static branch when X86_FEATURE_CLEAR_CPU_BUF is enabled. Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
2024-03-04x86/cpu: Use EXPORT_PER_CPU_SYMBOL_GPL() for x86_spec_ctrl_currentThomas Gleixner
Sparse rightfully complains: bugs.c:71:9: sparse: warning: incorrect type in initializer (different address spaces) bugs.c:71:9: sparse: expected void const [noderef] __percpu *__vpp_verify bugs.c:71:9: sparse: got unsigned long long * The reason is that x86_spec_ctrl_current which is a per CPU variable is exported with EXPORT_SYMBOL_GPL(). Use EXPORT_PER_CPU_SYMBOL_GPL() instead. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20240304005104.732288812@linutronix.de
2024-02-19x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static keyPawan Gupta
The VERW mitigation at exit-to-user is enabled via a static branch mds_user_clear. This static branch is never toggled after boot, and can be safely replaced with an ALTERNATIVE() which is convenient to use in asm. Switch to ALTERNATIVE() to use the VERW mitigation late in exit-to-user path. Also remove the now redundant VERW in exc_nmi() and arch_exit_to_user_mode(). Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Link: https://lore.kernel.org/all/20240213-delay-verw-v8-4-a6216d83edb7%40linux.intel.com
2024-02-12x86/retpoline: Ensure default return thunk isn't used at runtimeJosh Poimboeuf
Make sure the default return thunk is not used after all return instructions have been patched by the alternatives because the default return thunk is insufficient when it comes to mitigating Retbleed or SRSO. Fix based on an earlier version by David Kaplan <david.kaplan@amd.com>. [ bp: Fix the compilation error of warn_thunk_thunk being an invisible symbol, hoist thunk macro into calling.h ] Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Co-developed-by: Borislav Petkov (AMD) <bp@alien8.de> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20231010171020.462211-4-david.kaplan@amd.com Link: https://lore.kernel.org/r/20240104132446.GEZZaxnrIgIyat0pqf@fat_crate.local
2024-01-10x86/bugs: Rename CONFIG_CPU_SRSO => CONFIG_MITIGATION_SRSOBreno Leitao
Step 9/10 of the namespace unification of CPU mitigations related Kconfig options. Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231121160740.1249350-10-leitao@debian.org
2024-01-10x86/bugs: Rename CONFIG_CPU_IBRS_ENTRY => CONFIG_MITIGATION_IBRS_ENTRYBreno Leitao
Step 8/10 of the namespace unification of CPU mitigations related Kconfig options. Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231121160740.1249350-9-leitao@debian.org
2024-01-10x86/bugs: Rename CONFIG_CPU_UNRET_ENTRY => CONFIG_MITIGATION_UNRET_ENTRYBreno Leitao
Step 7/10 of the namespace unification of CPU mitigations related Kconfig options. Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231121160740.1249350-8-leitao@debian.org
2024-01-10x86/bugs: Rename CONFIG_RETPOLINE => CONFIG_MITIGATION_RETPOLINEBreno Leitao
Step 5/10 of the namespace unification of CPU mitigations related Kconfig options. [ mingo: Converted a few more uses in comments/messages as well. ] Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Ariel Miculas <amiculas@cisco.com> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231121160740.1249350-6-leitao@debian.org
2024-01-10x86/bugs: Rename CONFIG_CALL_DEPTH_TRACKING => ↵Breno Leitao
CONFIG_MITIGATION_CALL_DEPTH_TRACKING Step 3/10 of the namespace unification of CPU mitigations related Kconfig options. Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231121160740.1249350-4-leitao@debian.org
2024-01-10x86/bugs: Rename CONFIG_CPU_IBPB_ENTRY => CONFIG_MITIGATION_IBPB_ENTRYBreno Leitao
Step 2/10 of the namespace unification of CPU mitigations related Kconfig options. Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231121160740.1249350-3-leitao@debian.org
2024-01-10x86/bugs: Rename CONFIG_GDS_FORCE_MITIGATION => CONFIG_MITIGATION_GDS_FORCEBreno Leitao
So the CPU mitigations Kconfig entries - there's 10 meanwhile - are named in a historically idiosyncratic and hence rather inconsistent fashion and have become hard to relate with each other over the years: https://lore.kernel.org/lkml/20231011044252.42bplzjsam3qsasz@treble/ When they were introduced we never expected that we'd eventually have about a dozen of them, and that more organization would be useful, especially for Linux distributions that want to enable them in an informed fashion, and want to make sure all mitigations are configured as expected. For example, the current CONFIG_SPECULATION_MITIGATIONS namespace is only halfway populated, where some mitigations have entries in Kconfig, and they could be modified, while others mitigations do not have Kconfig entries, and can not be controlled at build time. Fine-grained control over these Kconfig entries can help in a number of ways: 1) Users can choose and pick only mitigations that are important for their workloads. 2) Users and developers can choose to disable mitigations that mangle the assembly code generation, making it hard to read. 3) Separate Kconfigs for just source code readability, so that we see *which* butt-ugly piece of crap code is for what reason... In most cases, if a mitigation is disabled at compilation time, it can still be enabled at runtime using kernel command line arguments. This is the first patch of an initial series that renames various mitigation related Kconfig options, unifying them under a single CONFIG_MITIGATION_* namespace: CONFIG_GDS_FORCE_MITIGATION => CONFIG_MITIGATION_GDS_FORCE CONFIG_CPU_IBPB_ENTRY => CONFIG_MITIGATION_IBPB_ENTRY CONFIG_CALL_DEPTH_TRACKING => CONFIG_MITIGATION_CALL_DEPTH_TRACKING CONFIG_PAGE_TABLE_ISOLATION => CONFIG_MITIGATION_PAGE_TABLE_ISOLATION CONFIG_RETPOLINE => CONFIG_MITIGATION_RETPOLINE CONFIG_SLS => CONFIG_MITIGATION_SLS CONFIG_CPU_UNRET_ENTRY => CONFIG_MITIGATION_UNRET_ENTRY CONFIG_CPU_IBRS_ENTRY => CONFIG_MITIGATION_IBRS_ENTRY CONFIG_CPU_SRSO => CONFIG_MITIGATION_SRSO CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK Implement step 1/10 of the namespace unification of CPU mitigations related Kconfig options and rename CONFIG_GDS_FORCE_MITIGATION to CONFIG_MITIGATION_GDS_FORCE. [ mingo: Rewrote changelog for clarity. ] Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231121160740.1249350-2-leitao@debian.org
2023-10-20x86/srso: Remove unnecessary semicolonYang Li
scripts/coccinelle/misc/semicolon.cocci reports: arch/x86/kernel/cpu/bugs.c:713:2-3: Unneeded semicolon Signed-off-by: Yang Li <yang.lee@linux.alibaba.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20230810010550.25733-1-yang.lee@linux.alibaba.com
2023-10-20x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()Josh Poimboeuf
For consistency with the other return thunks, rename __x86_return_skl() to call_depth_return_thunk(). Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/ae44e9f9976934e3b5b47a458d523ccb15867561.1693889988.git.jpoimboe@kernel.org
2023-10-20x86/srso: Disentangle rethunk-dependent optionsJosh Poimboeuf
CONFIG_RETHUNK, CONFIG_CPU_UNRET_ENTRY and CONFIG_CPU_SRSO are all tangled up. De-spaghettify the code a bit. Some of the rethunk-related code has been shuffled around within the '.text..__x86.return_thunk' section, but otherwise there are no functional changes. srso_alias_untrain_ret() and srso_alias_safe_ret() ((which are very address-sensitive) haven't moved. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/2845084ed303d8384905db3b87b77693945302b4.1693889988.git.jpoimboe@kernel.org
2023-10-20x86/srso: Move retbleed IBPB check into existing 'has_microcode' code blockJosh Poimboeuf
Simplify the code flow a bit by moving the retbleed IBPB check into the existing 'has_microcode' block. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/0a22b86b1f6b07f9046a9ab763fc0e0d1b7a91d4.1693889988.git.jpoimboe@kernel.org
2023-10-20x86/bugs: Remove default case for fully switched enumsJosh Poimboeuf
For enum switch statements which handle all possible cases, remove the default case so a compiler warning gets printed if one of the enums gets accidentally omitted from the switch statement. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/fcf6feefab991b72e411c2aed688b18e65e06aed.1693889988.git.jpoimboe@kernel.org
2023-10-20x86/srso: Remove 'pred_cmd' labelJosh Poimboeuf
SBPB is only enabled in two distinct cases: 1) when SRSO has been disabled with srso=off 2) when SRSO has been fixed (in future HW) Simplify the control flow by getting rid of the 'pred_cmd' label and moving the SBPB enablement check to the two corresponding code sites. This makes it more clear when exactly SBPB gets enabled. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/bb20e8569cfa144def5e6f25e610804bc4974de2.1693889988.git.jpoimboe@kernel.org
2023-10-20x86/srso: Fix vulnerability reporting for missing microcodeJosh Poimboeuf
The SRSO default safe-ret mitigation is reported as "mitigated" even if microcode hasn't been updated. That's wrong because userspace may still be vulnerable to SRSO attacks due to IBPB not flushing branch type predictions. Report the safe-ret + !microcode case as vulnerable. Also report the microcode-only case as vulnerable as it leaves the kernel open to attacks. Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/a8a14f97d1b0e03ec255c81637afdf4cf0ae9c99.1693889988.git.jpoimboe@kernel.org
2023-10-20x86/srso: Print mitigation for retbleed IBPB caseJosh Poimboeuf
When overriding the requested mitigation with IBPB due to retbleed=ibpb, print the mitigation in the usual format instead of a custom error message. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/ec3af919e267773d896c240faf30bfc6a1fd6304.1693889988.git.jpoimboe@kernel.org
2023-10-20x86/srso: Print actual mitigation if requested mitigation isn't possibleJosh Poimboeuf
If the kernel wasn't compiled to support the requested option, print the actual option that ends up getting used. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/7e7a12ea9d85a9f76ca16a3efb71f262dee46ab1.1693889988.git.jpoimboe@kernel.org
2023-10-20x86/srso: Fix SBPB enablement for (possible) future fixed HWJosh Poimboeuf
Make the SBPB check more robust against the (possible) case where future HW has SRSO fixed but doesn't have the SRSO_NO bit set. Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/cee5050db750b391c9f35f5334f8ff40e66c01b9.1693889988.git.jpoimboe@kernel.org
2023-09-19x86/srso: Fix SBPB enablement for spec_rstack_overflow=offJosh Poimboeuf
If the user has requested no SRSO mitigation, other mitigations can use the lighter-weight SBPB instead of IBPB. Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/b20820c3cfd1003171135ec8d762a0b957348497.1693889988.git.jpoimboe@kernel.org
2023-09-19x86/srso: Set CPUID feature bits independently of bug or mitigation statusJosh Poimboeuf
Booting with mitigations=off incorrectly prevents the X86_FEATURE_{IBPB_BRTYPE,SBPB} CPUID bits from getting set. Also, future CPUs without X86_BUG_SRSO might still have IBPB with branch type prediction flushing, in which case SBPB should be used instead of IBPB. The current code doesn't allow for that. Also, cpu_has_ibpb_brtype_microcode() has some surprising side effects and the setting of these feature bits really doesn't belong in the mitigation code anyway. Move it to earlier. Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Nikolay Borisov <nik.borisov@suse.com> Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/869a1709abfe13b673bdd10c2f4332ca253a40bc.1693889988.git.jpoimboe@kernel.org
2023-09-19x86/srso: Fix srso_show_state() side effectJosh Poimboeuf
Reading the 'spec_rstack_overflow' sysfs file can trigger an unnecessary MSR write, and possibly even a (handled) exception if the microcode hasn't been updated. Avoid all that by just checking X86_FEATURE_IBPB_BRTYPE instead, which gets set by srso_select_mitigation() if the updated microcode exists. Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Nikolay Borisov <nik.borisov@suse.com> Acked-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/27d128899cb8aee9eb2b57ddc996742b0c1d776b.1693889988.git.jpoimboe@kernel.org
2023-08-18x86/srso: Correct the mitigation status when SMT is disabledBorislav Petkov (AMD)
Specify how is SRSO mitigated when SMT is disabled. Also, correct the SMT check for that. Fixes: e9fbc47b818b ("x86/srso: Disable the mitigation on unaffected configurations") Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Link: https://lore.kernel.org/r/20230814200813.p5czl47zssuej7nv@treble
2023-08-16x86/cpu/kvm: Provide UNTRAIN_RET_VMPeter Zijlstra
Similar to how it doesn't make sense to have UNTRAIN_RET have two untrain calls, it also doesn't make sense for VMEXIT to have an extra IBPB call. This cures VMEXIT doing potentially unret+IBPB or double IBPB. Also, the (SEV) VMEXIT case seems to have been overlooked. Redefine the meaning of the synthetic IBPB flags to: - ENTRY_IBPB -- issue IBPB on entry (was: entry + VMEXIT) - IBPB_ON_VMEXIT -- issue IBPB on VMEXIT And have 'retbleed=ibpb' set *BOTH* feature flags to ensure it retains the previous behaviour and issues IBPB on entry+VMEXIT. The new 'srso=ibpb_vmexit' option only sets IBPB_ON_VMEXIT. Create UNTRAIN_RET_VM specifically for the VMEXIT case, and have that check IBPB_ON_VMEXIT. All this avoids having the VMEXIT case having to check both ENTRY_IBPB and IBPB_ON_VMEXIT and simplifies the alternatives. Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20230814121149.109557833@infradead.org
2023-08-16x86/cpu: Cleanup the untrain messPeter Zijlstra
Since there can only be one active return_thunk, there only needs be one (matching) untrain_ret. It fundamentally doesn't make sense to allow multiple untrain_ret at the same time. Fold all the 3 different untrain methods into a single (temporary) helper stub. Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20230814121149.042774962@infradead.org
2023-08-16x86/cpu: Rename original retbleed methodsPeter Zijlstra
Rename the original retbleed return thunk and untrain_ret to retbleed_return_thunk() and retbleed_untrain_ret(). No functional changes. Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20230814121148.909378169@infradead.org
2023-08-16x86/cpu: Clean up SRSO return thunk messPeter Zijlstra
Use the existing configurable return thunk. There is absolute no justification for having created this __x86_return_thunk alternative. To clarify, the whole thing looks like: Zen3/4 does: srso_alias_untrain_ret: nop2 lfence jmp srso_alias_return_thunk int3 srso_alias_safe_ret: // aliasses srso_alias_untrain_ret just so add $8, %rsp ret int3 srso_alias_return_thunk: call srso_alias_safe_ret ud2 While Zen1/2 does: srso_untrain_ret: movabs $foo, %rax lfence call srso_safe_ret (jmp srso_return_thunk ?) int3 srso_safe_ret: // embedded in movabs instruction add $8,%rsp ret int3 srso_return_thunk: call srso_safe_ret ud2 While retbleed does: zen_untrain_ret: test $0xcc, %bl lfence jmp zen_return_thunk int3 zen_return_thunk: // embedded in the test instruction ret int3 Where Zen1/2 flush the BTB entry using the instruction decoder trick (test,movabs) Zen3/4 use BTB aliasing. SRSO adds a return sequence (srso_safe_ret()) which forces the function return instruction to speculate into a trap (UD2). This RET will then mispredict and execution will continue at the return site read from the top of the stack. Pick one of three options at boot (evey function can only ever return once). [ bp: Fixup commit message uarch details and add them in a comment in the code too. Add a comment about the srso_select_mitigation() dependency on retbleed_select_mitigation(). Add moar ifdeffery for 32-bit builds. Add a dummy srso_untrain_ret_alias() definition for 32-bit alternatives needing the symbol. ] Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20230814121148.842775684@infradead.org
2023-08-16x86/alternative: Make custom return thunk unconditionalPeter Zijlstra
There is infrastructure to rewrite return thunks to point to any random thunk one desires, unwrap that from CALL_THUNKS, which up to now was the sole user of that. [ bp: Make the thunks visible on 32-bit and add ifdeffery for the 32-bit builds. ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20230814121148.775293785@infradead.org
2023-08-14x86/srso: Disable the mitigation on unaffected configurationsBorislav Petkov (AMD)
Skip the srso cmd line parsing which is not needed on Zen1/2 with SMT disabled and with the proper microcode applied (latter should be the case anyway) as those are not affected. Fixes: 5a15d8348881 ("x86/srso: Tie SBPB bit setting to microcode patch detection") Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20230813104517.3346-1-bp@alien8.de
2023-08-07Merge tag 'gds-for-linus-2023-08-01' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86/gds fixes from Dave Hansen: "Mitigate Gather Data Sampling issue: - Add Base GDS mitigation - Support GDS_NO under KVM - Fix a documentation typo" * tag 'gds-for-linus-2023-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: Documentation/x86: Fix backwards on/off logic about YMM support KVM: Add GDS_NO support to KVM x86/speculation: Add Kconfig option for GDS x86/speculation: Add force option to GDS mitigation x86/speculation: Add Gather Data Sampling mitigation
2023-08-07Merge tag 'x86_bugs_srso' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86/srso fixes from Borislav Petkov: "Add a mitigation for the speculative RAS (Return Address Stack) overflow vulnerability on AMD processors. In short, this is yet another issue where userspace poisons a microarchitectural structure which can then be used to leak privileged information through a side channel" * tag 'x86_bugs_srso' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/srso: Tie SBPB bit setting to microcode patch detection x86/srso: Add a forgotten NOENDBR annotation x86/srso: Fix return thunks in generated code x86/srso: Add IBPB on VMEXIT x86/srso: Add IBPB x86/srso: Add SRSO_NO support x86/srso: Add IBPB_BRTYPE support x86/srso: Add a Speculative RAS Overflow mitigation x86/bugs: Increase the x86 bugs vector size to two u32s
2023-08-07x86/srso: Tie SBPB bit setting to microcode patch detectionBorislav Petkov (AMD)
The SBPB bit in MSR_IA32_PRED_CMD is supported only after a microcode patch has been applied so set X86_FEATURE_SBPB only then. Otherwise, guests would attempt to set that bit and #GP on the MSR write. While at it, make SMT detection more robust as some guests - depending on how and what CPUID leafs their report - lead to cpu_smt_control getting set to CPU_SMT_NOT_SUPPORTED but SRSO_NO should be set for any guest incarnation where one simply cannot do SMT, for whatever reason. Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Reported-by: Salvatore Bonaccorso <carnil@debian.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
2023-07-29x86/srso: Fix return thunks in generated codeJosh Poimboeuf
Set X86_FEATURE_RETHUNK when enabling the SRSO mitigation so that generated code (e.g., ftrace, static call, eBPF) generates "jmp __x86_return_thunk" instead of RET. [ bp: Add a comment. ] Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
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