kernel.git/arch/x86/kernel/fpu, branch linux-6.0.y

x86/fpu/xstate: Fix XSTATE_WARN_ON() to emit relevant diagnostics

2023-01-07T10:15:45Z

commit 48280042f2c6e3ac2cfb1d8b752ab4a7e0baea24 upstream. "XSAVE consistency problem" has been reported under Xen, but that's the extent of my divination skills. Modify XSTATE_WARN_ON() to force the caller to provide relevant diagnostic information, and modify each caller suitably. For check_xstate_against_struct(), this removes a double WARN() where one will do perfectly fine. CC stable as this has been wonky debugging for 7 years and it is good to have there too. Signed-off-by: Andrew Cooper Signed-off-by: Borislav Petkov Cc: Link: https://lore.kernel.org/r/20220810221909.12768-1-andrew.cooper3@citrix.com Signed-off-by: Greg Kroah-Hartman

x86/fpu: Drop fpregs lock before inheriting FPU permissions

2022-11-26T08:27:51Z

commit 36b038791e1e2baea892e9276588815fd14894b4 upstream. Mike Galbraith reported the following against an old fork of preempt-rt but the same issue also applies to the current preempt-rt tree. BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: systemd preempt_count: 1, expected: 0 RCU nest depth: 0, expected: 0 Preemption disabled at: fpu_clone CPU: 6 PID: 1 Comm: systemd Tainted: G E (unreleased) Call Trace: dump_stack_lvl ? fpu_clone __might_resched rt_spin_lock fpu_clone ? copy_thread ? copy_process ? shmem_alloc_inode ? kmem_cache_alloc ? kernel_clone ? __do_sys_clone ? do_syscall_64 ? __x64_sys_rt_sigprocmask ? syscall_exit_to_user_mode ? do_syscall_64 ? syscall_exit_to_user_mode ? do_syscall_64 ? syscall_exit_to_user_mode ? do_syscall_64 ? exc_page_fault ? entry_SYSCALL_64_after_hwframe Mike says: The splat comes from fpu_inherit_perms() being called under fpregs_lock(), and us reaching the spin_lock_irq() therein due to fpu_state_size_dynamic() returning true despite static key __fpu_state_size_dynamic having never been enabled. Mike's assessment looks correct. fpregs_lock on a PREEMPT_RT kernel disables preemption so calling spin_lock_irq() in fpu_inherit_perms() is unsafe. This problem exists since commit 9e798e9aa14c ("x86/fpu: Prepare fpu_clone() for dynamically enabled features"). Even though the original bug report should not have enabled the paths at all, the bug still exists. fpregs_lock is necessary when editing the FPU registers or a task's FP state but it is not necessary for fpu_inherit_perms(). The only write of any FP state in fpu_inherit_perms() is for the new child which is not running yet and cannot context switch or be borrowed by a kernel thread yet. Hence, fpregs_lock is not protecting anything in the new child until clone() completes and can be dropped earlier. The siglock still needs to be acquired by fpu_inherit_perms() as the read of the parent's permissions has to be serialised. [ bp: Cleanup splat. ] Fixes: 9e798e9aa14c ("x86/fpu: Prepare fpu_clone() for dynamically enabled features") Reported-by: Mike Galbraith Signed-off-by: Mel Gorman Signed-off-by: Borislav Petkov Reviewed-by: Thomas Gleixner Cc: Link: https://lore.kernel.org/r/20221110124400.zgymc2lnwqjukgfh@techsingularity.net Signed-off-by: Greg Kroah-Hartman

x86/fpu: Fix copy_xstate_to_uabi() to copy init states correctly

2022-11-03T15:00:30Z

[ Upstream commit 471f0aa7fa64e23766a1473b32d9ec3f0718895a ] When an extended state component is not present in fpstate, but in init state, the function copies from init_fpstate via copy_feature(). But, dynamic states are not present in init_fpstate because of all-zeros init states. Then retrieving them from init_fpstate will explode like this: BUG: kernel NULL pointer dereference, address: 0000000000000000 ... RIP: 0010:memcpy_erms+0x6/0x10 ? __copy_xstate_to_uabi_buf+0x381/0x870 fpu_copy_guest_fpstate_to_uabi+0x28/0x80 kvm_arch_vcpu_ioctl+0x14c/0x1460 [kvm] ? __this_cpu_preempt_check+0x13/0x20 ? vmx_vcpu_put+0x2e/0x260 [kvm_intel] kvm_vcpu_ioctl+0xea/0x6b0 [kvm] ? kvm_vcpu_ioctl+0xea/0x6b0 [kvm] ? __fget_light+0xd4/0x130 __x64_sys_ioctl+0xe3/0x910 ? debug_smp_processor_id+0x17/0x20 ? fpregs_assert_state_consistent+0x27/0x50 do_syscall_64+0x3f/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Adjust the 'mask' to zero out the userspace buffer for the features that are not available both from fpstate and from init_fpstate. The dynamic features depend on the compacted XSAVE format. Ensure it is enabled before reading XCOMP_BV in init_fpstate. Fixes: 2308ee57d93d ("x86/fpu/amx: Enable the AMX feature in 64-bit mode") Reported-by: Yuan Yao Suggested-by: Dave Hansen Signed-off-by: Chang S. Bae Signed-off-by: Dave Hansen Tested-by: Yuan Yao Link: https://lore.kernel.org/lkml/BYAPR11MB3717EDEF2351C958F2C86EED95259@BYAPR11MB3717.namprd11.prod.outlook.com/ Link: https://lkml.kernel.org/r/20221021185844.13472-1-chang.seok.bae@intel.com Signed-off-by: Sasha Levin

x86/fpu: Exclude dynamic states from init_fpstate

2022-11-03T15:00:27Z

[ Upstream commit a401f45e38754953c9d402f8b3bc965707eecc91 ] == Background == The XSTATE init code initializes all enabled and supported components. Then, the init states are saved in the init_fpstate buffer that is statically allocated in about one page. The AMX TILE_DATA state is large (8KB) but its init state is zero. And the feature comes only with the compacted format with these established dependencies: AMX->XFD->XSAVES. So this state is excludable from init_fpstate. == Problem == But the buffer is formatted to include that large state. Then, this can be the cause of a noisy splat like the below. This came from XRSTORS for the task with init_fpstate in its XSAVE buffer. It is reproducible on AMX systems when the running kernel is built with CONFIG_DEBUG_PAGEALLOC=y and CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT=y: Bad FPU state detected at restore_fpregs_from_fpstate+0x57/0xd0, reinitializing FPU registers. ... RIP: 0010:restore_fpregs_from_fpstate+0x57/0xd0 ? restore_fpregs_from_fpstate+0x45/0xd0 switch_fpu_return+0x4e/0xe0 exit_to_user_mode_prepare+0x17b/0x1b0 syscall_exit_to_user_mode+0x29/0x40 do_syscall_64+0x67/0x80 ? do_syscall_64+0x67/0x80 ? exc_page_fault+0x86/0x180 entry_SYSCALL_64_after_hwframe+0x63/0xcd == Solution == Adjust init_fpstate to exclude dynamic states. XRSTORS from init_fpstate still initializes those states when their bits are set in the requested-feature bitmap. Fixes: 2308ee57d93d ("x86/fpu/amx: Enable the AMX feature in 64-bit mode") Reported-by: Lin X Wang Signed-off-by: Chang S. Bae Signed-off-by: Thomas Gleixner Tested-by: Lin X Wang Link: https://lore.kernel.org/r/20220824191223.1248-4-chang.seok.bae@intel.com Signed-off-by: Sasha Levin

x86/fpu: Fix the init_fpstate size check with the actual size

2022-11-03T15:00:27Z

[ Upstream commit d3e021adac7c51a26d9ede167c789fcc1b878467 ] The init_fpstate buffer is statically allocated. Thus, the sanity test was established to check whether the pre-allocated buffer is enough for the calculated size or not. The currently measured size is not strictly relevant. Fix to validate the calculated init_fpstate size with the pre-allocated area. Also, replace the sanity check function with open code for clarity. The abstraction itself and the function naming do not tend to represent simply what it does. Fixes: 2ae996e0c1a3 ("x86/fpu: Calculate the default sizes independently") Signed-off-by: Chang S. Bae Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220824191223.1248-3-chang.seok.bae@intel.com Signed-off-by: Sasha Levin

x86/fpu: Configure init_fpstate attributes orderly

2022-11-03T15:00:27Z

[ Upstream commit c32d7cab57e3a77af8ecc17cde7a5761a26483b8 ] The init_fpstate setup code is spread out and out of order. The init image is recorded before its scoped features and the buffer size are determined. Determine the scope of init_fpstate components and its size before recording the init state. Also move the relevant code together. Signed-off-by: Chang S. Bae Signed-off-by: Thomas Gleixner Acked-by: neelnatu@google.com Link: https://lore.kernel.org/r/20220824191223.1248-2-chang.seok.bae@intel.com Stable-dep-of: d3e021adac7c ("x86/fpu: Fix the init_fpstate size check with the actual size") Signed-off-by: Sasha Levin

x86/fpu: Add a helper to prepare AMX state for low-power CPU idle

2022-07-19T16:46:15Z

When a CPU enters an idle state, a non-initialized AMX register state may be the cause of preventing a deeper low-power state. Other extended register states whether initialized or not do not impact the CPU idle state. The new helper can ensure the AMX state is initialized before the CPU is idle, and it will be used by the intel idle driver. Check the AMX_TILE feature bit before using XGETBV1 as a chain of dependencies was established via cpuid_deps[]: AMX->XFD->XGETBV1. Signed-off-by: Chang S. Bae Signed-off-by: Dave Hansen Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20220608164748.11864-2-chang.seok.bae@intel.com

Merge tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2022-06-03T23:03:05Z

Pull kthread updates from Eric Biederman: "This updates init and user mode helper tasks to be ordinary user mode tasks. Commit 40966e316f86 ("kthread: Ensure struct kthread is present for all kthreads") caused init and the user mode helper threads that call kernel_execve to have struct kthread allocated for them. This struct kthread going away during execve in turned made a use after free of struct kthread possible. Here, commit 343f4c49f243 ("kthread: Don't allocate kthread_struct for init and umh") is enough to fix the use after free and is simple enough to be backportable. The rest of the changes pass struct kernel_clone_args to clean things up and cause the code to make sense. In making init and the user mode helpers tasks purely user mode tasks I ran into two complications. The function task_tick_numa was detecting tasks without an mm by testing for the presence of PF_KTHREAD. The initramfs code in populate_initrd_image was using flush_delayed_fput to ensuere the closing of all it's file descriptors was complete, and flush_delayed_fput does not work in a userspace thread. I have looked and looked and more complications and in my code review I have not found any, and neither has anyone else with the code sitting in linux-next" * tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: sched: Update task_tick_numa to ignore tasks without an mm fork: Stop allowing kthreads to call execve fork: Explicitly set PF_KTHREAD init: Deal with the init process being a user mode process fork: Generalize PF_IO_WORKER handling fork: Explicity test for idle tasks in copy_thread fork: Pass struct kernel_clone_args into copy_thread kthread: Don't allocate kthread_struct for init and umh

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2022-05-26T21:20:14Z

Pull kvm updates from Paolo Bonzini: "S390: - ultravisor communication device driver - fix TEID on terminating storage key ops RISC-V: - Added Sv57x4 support for G-stage page table - Added range based local HFENCE functions - Added remote HFENCE functions based on VCPU requests - Added ISA extension registers in ONE_REG interface - Updated KVM RISC-V maintainers entry to cover selftests support ARM: - Add support for the ARMv8.6 WFxT extension - Guard pages for the EL2 stacks - Trap and emulate AArch32 ID registers to hide unsupported features - Ability to select and save/restore the set of hypercalls exposed to the guest - Support for PSCI-initiated suspend in collaboration with userspace - GICv3 register-based LPI invalidation support - Move host PMU event merging into the vcpu data structure - GICv3 ITS save/restore fixes - The usual set of small-scale cleanups and fixes x86: - New ioctls to get/set TSC frequency for a whole VM - Allow userspace to opt out of hypercall patching - Only do MSR filtering for MSRs accessed by rdmsr/wrmsr AMD SEV improvements: - Add KVM_EXIT_SHUTDOWN metadata for SEV-ES - V_TSC_AUX support Nested virtualization improvements for AMD: - Support for "nested nested" optimizations (nested vVMLOAD/VMSAVE, nested vGIF) - Allow AVIC to co-exist with a nested guest running - Fixes for LBR virtualizations when a nested guest is running, and nested LBR virtualization support - PAUSE filtering for nested hypervisors Guest support: - Decoupling of vcpu_is_preempted from PV spinlocks" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (199 commits) KVM: x86: Fix the intel_pt PMI handling wrongly considered from guest KVM: selftests: x86: Sync the new name of the test case to .gitignore Documentation: kvm: reorder ARM-specific section about KVM_SYSTEM_EVENT_SUSPEND x86, kvm: use correct GFP flags for preemption disabled KVM: LAPIC: Drop pending LAPIC timer injection when canceling the timer x86/kvm: Alloc dummy async #PF token outside of raw spinlock KVM: x86: avoid calling x86 emulator without a decoded instruction KVM: SVM: Use kzalloc for sev ioctl interfaces to prevent kernel data leak x86/fpu: KVM: Set the base guest FPU uABI size to sizeof(struct kvm_xsave) s390/uv_uapi: depend on CONFIG_S390 KVM: selftests: x86: Fix test failure on arch lbr capable platforms KVM: LAPIC: Trace LAPIC timer expiration on every vmentry KVM: s390: selftest: Test suppression indication on key prot exception KVM: s390: Don't indicate suppression on dirtying, failing memop selftests: drivers/s390x: Add uvdevice tests drivers/s390/char: Add Ultravisor io device MAINTAINERS: Update KVM RISC-V entry to cover selftests support RISC-V: KVM: Introduce ISA extension register RISC-V: KVM: Cleanup stale TLB entries when host CPU changes RISC-V: KVM: Add remote HFENCE functions based on VCPU requests ...

x86/fpu: KVM: Set the base guest FPU uABI size to sizeof(struct kvm_xsave)

2022-05-25T09:11:37Z

Set the starting uABI size of KVM's guest FPU to 'struct kvm_xsave', i.e. to KVM's historical uABI size. When saving FPU state for usersapce, KVM (well, now the FPU) sets the FP+SSE bits in the XSAVE header even if the host doesn't support XSAVE. Setting the XSAVE header allows the VM to be migrated to a host that does support XSAVE without the new host having to handle FPU state that may or may not be compatible with XSAVE. Setting the uABI size to the host's default size results in out-of-bounds writes (setting the FP+SSE bits) and data corruption (that is thankfully caught by KASAN) when running on hosts without XSAVE, e.g. on Core2 CPUs. WARN if the default size is larger than KVM's historical uABI size; all features that can push the FPU size beyond the historical size must be opt-in. ================================================================== BUG: KASAN: slab-out-of-bounds in fpu_copy_uabi_to_guest_fpstate+0x86/0x130 Read of size 8 at addr ffff888011e33a00 by task qemu-build/681 CPU: 1 PID: 681 Comm: qemu-build Not tainted 5.18.0-rc5-KASAN-amd64 #1 Hardware name: /DG35EC, BIOS ECG3510M.86A.0118.2010.0113.1426 01/13/2010 Call Trace: dump_stack_lvl+0x34/0x45 print_report.cold+0x45/0x575 kasan_report+0x9b/0xd0 fpu_copy_uabi_to_guest_fpstate+0x86/0x130 kvm_arch_vcpu_ioctl+0x72a/0x1c50 [kvm] kvm_vcpu_ioctl+0x47f/0x7b0 [kvm] __x64_sys_ioctl+0x5de/0xc90 do_syscall_64+0x31/0x50 entry_SYSCALL_64_after_hwframe+0x44/0xae Allocated by task 0: (stack is not available) The buggy address belongs to the object at ffff888011e33800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes to the right of 512-byte region [ffff888011e33800, ffff888011e33a00) The buggy address belongs to the physical page: page:0000000089cd4adb refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11e30 head:0000000089cd4adb order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head|zone=1) raw: 4000000000010200 dead000000000100 dead000000000122 ffff888001041c80 raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888011e33900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888011e33980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff888011e33a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff888011e33a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888011e33b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== Disabling lock debugging due to kernel taint Fixes: be50b2065dfa ("kvm: x86: Add support for getting/setting expanded xstate buffer") Fixes: c60427dd50ba ("x86/fpu: Add uabi_size to guest_fpu") Reported-by: Zdenek Kaspar Cc: Maciej S. Szmigiero Cc: Paolo Bonzini Cc: kvm@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Tested-by: Zdenek Kaspar Message-Id: <20220504001219.983513-1-seanjc@google.com> Signed-off-by: Paolo Bonzini