user/sven/linux.git/Documentation, branch v6.1.87

x86/bugs: Remove CONFIG_BHI_MITIGATION_AUTO and spectre_bhi=auto

2024-04-17T09:18:29Z

commit 36d4fe147c870f6d3f6602befd7ef44393a1c87a upstream. 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 Signed-off-by: Ingo Molnar Reviewed-by: Nikolay Borisov Cc: Sean Christopherson Cc: Linus Torvalds Link: https://lore.kernel.org/r/412e9dc87971b622bbbaf64740ebc1f140bff343.1712813475.git.jpoimboe@kernel.org Signed-off-by: Greg Kroah-Hartman

x86/bugs: Clarify that syscall hardening isn't a BHI mitigation

2024-04-17T09:18:28Z

commit 5f882f3b0a8bf0788d5a0ee44b1191de5319bb8a upstream. 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 Signed-off-by: Ingo Molnar Cc: Linus Torvalds Cc: Sean Christopherson Link: https://lore.kernel.org/r/b5951dae3fdee7f1520d5136a27be3bdfe95f88b.1712813475.git.jpoimboe@kernel.org Signed-off-by: Greg Kroah-Hartman

x86/bugs: Fix BHI documentation

2024-04-17T09:18:28Z

commit dfe648903f42296866d79f10d03f8c85c9dfba30 upstream. Fix up some inaccuracies in the BHI documentation. Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Reviewed-by: Nikolay Borisov Cc: Linus Torvalds Cc: Sean Christopherson Link: https://lore.kernel.org/r/8c84f7451bfe0dd08543c6082a383f390d4aa7e2.1712813475.git.jpoimboe@kernel.org Signed-off-by: Greg Kroah-Hartman

x86/bhi: Mitigate KVM by default

2024-04-10T14:28:35Z

commit 95a6ccbdc7199a14b71ad8901cb788ba7fb5167b upstream. 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 Signed-off-by: Pawan Gupta Signed-off-by: Daniel Sneddon Signed-off-by: Thomas Gleixner Reviewed-by: Alexandre Chartre Reviewed-by: Josh Poimboeuf Signed-off-by: Daniel Sneddon Signed-off-by: Greg Kroah-Hartman

x86/bhi: Add BHI mitigation knob

2024-04-10T14:28:35Z

commit ec9404e40e8f36421a2b66ecb76dc2209fe7f3ef upstream. 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 Signed-off-by: Daniel Sneddon Signed-off-by: Thomas Gleixner Reviewed-by: Alexandre Chartre Reviewed-by: Josh Poimboeuf Signed-off-by: Daniel Sneddon Signed-off-by: Greg Kroah-Hartman

x86/cpu: Enable STIBP on AMD if Automatic IBRS is enabled

2024-04-03T13:19:54Z

commit fd470a8beed88440b160d690344fbae05a0b9b1b upstream. Unlike Intel's Enhanced IBRS feature, AMD's Automatic IBRS does not provide protection to processes running at CPL3/user mode, see section "Extended Feature Enable Register (EFER)" in the APM v2 at https://bugzilla.kernel.org/attachment.cgi?id=304652 Explicitly enable STIBP to protect against cross-thread CPL3 branch target injections on systems with Automatic IBRS enabled. Also update the relevant documentation. Fixes: e7862eda309e ("x86/cpu: Support AMD Automatic IBRS") Reported-by: Tom Lendacky Signed-off-by: Kim Phillips Signed-off-by: Borislav Petkov (AMD) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230720194727.67022-1-kim.phillips@amd.com Signed-off-by: Greg Kroah-Hartman

x86/Kconfig: Remove CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT

2024-04-03T13:19:47Z

commit 29956748339aa8757a7e2f927a8679dd08f24bb6 upstream. It was meant well at the time but nothing's using it so get rid of it. Signed-off-by: Borislav Petkov (AMD) Acked-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20240202163510.GDZb0Zvj8qOndvFOiZ@fat_crate.local Signed-off-by: Ard Biesheuvel Signed-off-by: Greg Kroah-Hartman

media: mc: Expand MUST_CONNECT flag to always require an enabled link

2024-04-03T13:19:25Z

[ Upstream commit b3decc5ce7d778224d266423b542326ad469cb5f ] The MEDIA_PAD_FL_MUST_CONNECT flag indicates that the pad requires an enabled link to stream, but only if it has any link at all. This makes little sense, as if a pad is part of a pipeline, there are very few use cases for an active link to be mandatory only if links exist at all. A review of in-tree drivers confirms they all need an enabled link for pads marked with the MEDIA_PAD_FL_MUST_CONNECT flag. Expand the scope of the flag by rejecting pads that have no links at all. This requires modifying the pipeline build code to add those pads to the pipeline. Cc: stable@vger.kernel.org # 6.1 Signed-off-by: Laurent Pinchart Acked-by: Sakari Ailus Signed-off-by: Hans Verkuil Signed-off-by: Sasha Levin

x86/cpu: Support AMD Automatic IBRS

2024-04-03T13:19:22Z

commit e7862eda309ecfccc36bb5558d937ed3ace07f3f upstream. The AMD Zen4 core supports a new feature called Automatic IBRS. It is a "set-and-forget" feature that means that, like Intel's Enhanced IBRS, h/w manages its IBRS mitigation resources automatically across CPL transitions. The feature is advertised by CPUID_Fn80000021_EAX bit 8 and is enabled by setting MSR C000_0080 (EFER) bit 21. Enable Automatic IBRS by default if the CPU feature is present. It typically provides greater performance over the incumbent generic retpolines mitigation. Reuse the SPECTRE_V2_EIBRS spectre_v2_mitigation enum. AMD Automatic IBRS and Intel Enhanced IBRS have similar enablement. Add NO_EIBRS_PBRSB to cpu_vuln_whitelist, since AMD Automatic IBRS isn't affected by PBRSB-eIBRS. The kernel command line option spectre_v2=eibrs is used to select AMD Automatic IBRS, if available. Signed-off-by: Kim Phillips Signed-off-by: Borislav Petkov (AMD) Acked-by: Sean Christopherson Acked-by: Dave Hansen Link: https://lore.kernel.org/r/20230124163319.2277355-8-kim.phillips@amd.com Signed-off-by: Greg Kroah-Hartman

x86/rfds: Mitigate Register File Data Sampling (RFDS)

2024-03-15T14:48:21Z

commit 8076fcde016c9c0e0660543e67bff86cb48a7c9c upstream. 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 Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner Acked-by: Josh Poimboeuf Signed-off-by: Greg Kroah-Hartman