kernel/linux.git/virt, branch linux-6.9.y

virt: guest_memfd: fix reference leak on hwpoisoned page

2024-06-27T11:52:31+00:00

commit c31745d2c508796a0996c88bf2e55f552d513f65 upstream. If kvm_gmem_get_pfn() detects an hwpoisoned page, it returns -EHWPOISON but it does not put back the reference that kvm_gmem_get_folio() had grabbed. Add the forgotten folio_put(). Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory") Cc: stable@vger.kernel.org Reviewed-by: Liam Merwick Reviewed-by: Isaku Yamahata Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin()

2024-06-27T11:52:27+00:00

commit 49f683b41f28918df3e51ddc0d928cb2e934ccdb upstream. Use {READ,WRITE}_ONCE() to access kvm->last_boosted_vcpu to ensure the loads and stores are atomic. In the extremely unlikely scenario the compiler tears the stores, it's theoretically possible for KVM to attempt to get a vCPU using an out-of-bounds index, e.g. if the write is split into multiple 8-bit stores, and is paired with a 32-bit load on a VM with 257 vCPUs: CPU0 CPU1 last_boosted_vcpu = 0xff; (last_boosted_vcpu = 0x100) last_boosted_vcpu[15:8] = 0x01; i = (last_boosted_vcpu = 0x1ff) last_boosted_vcpu[7:0] = 0x00; vcpu = kvm->vcpu_array[0x1ff]; As detected by KCSAN: BUG: KCSAN: data-race in kvm_vcpu_on_spin [kvm] / kvm_vcpu_on_spin [kvm] write to 0xffffc90025a92344 of 4 bytes by task 4340 on cpu 16: kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4112) kvm handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:? arch/x86/kvm/vmx/vmx.c:6606) kvm_intel vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890) __x64_sys_ioctl (fs/ioctl.c:890) x64_sys_call (arch/x86/entry/syscall_64.c:33) do_syscall_64 (arch/x86/entry/common.c:?) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) read to 0xffffc90025a92344 of 4 bytes by task 4342 on cpu 4: kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4069) kvm handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:? arch/x86/kvm/vmx/vmx.c:6606) kvm_intel vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890) __x64_sys_ioctl (fs/ioctl.c:890) x64_sys_call (arch/x86/entry/syscall_64.c:33) do_syscall_64 (arch/x86/entry/common.c:?) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) value changed: 0x00000012 -> 0x00000000 Fixes: 217ece6129f2 ("KVM: use yield_to instead of sleep in kvm_vcpu_on_spin") Cc: stable@vger.kernel.org Signed-off-by: Breno Leitao Link: https://lore.kernel.org/r/20240510092353.2261824-1-leitao@debian.org Signed-off-by: Sean Christopherson Signed-off-by: Greg Kroah-Hartman

KVM: Drop unused @may_block param from gfn_to_pfn_cache_invalidate_start()

2024-04-11T19:58:53+00:00

Remove gfn_to_pfn_cache_invalidate_start()'s unused @may_block parameter, which was leftover from KVM's abandoned (for now) attempt to support guest usage of gfn_to_pfn caches. Fixes: a4bff3df5147 ("KVM: pfncache: remove KVM_GUEST_USES_PFN usage") Reported-by: Like Xu Cc: Paul Durrant Cc: David Woodhouse Reviewed-by: Paul Durrant Reviewed-by: David Woodhouse Link: https://lore.kernel.org/r/20240305003742.245767-1-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: Explicitly disallow activatating a gfn_to_pfn_cache with INVALID_GPA

2024-04-08T20:20:24+00:00

Explicit disallow activating a gfn_to_pfn_cache with an error gpa, i.e. INVALID_GPA, to ensure that KVM doesn't mistake a GPA-based cache for an HVA-based cache (KVM uses INVALID_GPA as a magic value to differentiate between GPA-based and HVA-based caches). WARN if KVM attempts to activate a cache with INVALID_GPA, purely so that new caches need to at least consider what to do with a "bad" GPA, as all existing usage of kvm_gpc_activate() guarantees gpa != INVALID_GPA. I.e. removing the WARN in the future is completely reasonable if doing so would yield cleaner/better code overall. Reviewed-by: David Woodhouse Reviewed-by: Paul Durrant Link: https://lore.kernel.org/r/20240320001542.3203871-4-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: Check validity of offset+length of gfn_to_pfn_cache prior to activation

2024-04-08T20:20:24+00:00

When activating a gfn_to_pfn_cache, verify that the offset+length is sane and usable before marking the cache active. Letting __kvm_gpc_refresh() detect the problem results in a cache being marked active without setting the GPA (or any other fields), which in turn results in KVM trying to refresh a cache with INVALID_GPA. Attempting to refresh a cache with INVALID_GPA isn't functionally problematic, but it runs afoul of the sanity check that exactly one of GPA or userspace HVA is valid, i.e. that a cache is either GPA-based or HVA-based. Reported-by: syzbot+106a4f72b0474e1d1b33@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/0000000000005fa5cc0613f1cebd@google.com Fixes: 721f5b0dda78 ("KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA") Cc: David Woodhouse Cc: Paul Durrant Reviewed-by: Paul Durrant Reviewed-by: David Woodhouse Link: https://lore.kernel.org/r/20240320001542.3203871-3-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: Add helpers to consolidate gfn_to_pfn_cache's page split check

2024-04-08T20:20:23+00:00

Add a helper to check that the incoming length for a gfn_to_pfn_cache is valid with respect to the cache's GPA and/or HVA. To avoid activating a cache with a bogus GPA, a future fix will fork the page split check in the inner refresh path into activate() and the public rerfresh() APIs, at which point KVM will check the length in three separate places. Deliberately keep the "page offset" logic open coded, as the only other path that consumes the offset, __kvm_gpc_refresh(), already needs to differentiate between GPA-based and HVA-based caches, and it's not obvious that using a helper is a net positive in overall code readability. Note, for GPA-based caches, this has a subtle side effect of using the GPA instead of the resolved HVA in the check() path, but that should be a nop as the HVA offset is derived from the GPA, i.e. the two offsets are identical, barring a KVM bug. Reviewed-by: Paul Durrant Reviewed-by: David Woodhouse Link: https://lore.kernel.org/r/20240320001542.3203871-2-seanjc@google.com Signed-off-by: Sean Christopherson

Merge tag 'kvm-x86-xen-6.9' of https://github.com/kvm-x86/linux into HEAD

2024-03-11T14:42:55+00:00

KVM Xen and pfncache changes for 6.9: - Rip out the half-baked support for using gfn_to_pfn caches to manage pages that are "mapped" into guests via physical addresses. - Add support for using gfn_to_pfn caches with only a host virtual address, i.e. to bypass the "gfn" stage of the cache. The primary use case is overlay pages, where the guest may change the gfn used to reference the overlay page, but the backing hva+pfn remains the same. - Add an ioctl() to allow mapping Xen's shared_info page using an hva instead of a gpa, so that userspace doesn't need to reconfigure and invalidate the cache/mapping if the guest changes the gpa (but userspace keeps the resolved hva the same). - When possible, use a single host TSC value when computing the deadline for Xen timers in order to improve the accuracy of the timer emulation. - Inject pending upcall events when the vCPU software-enables its APIC to fix a bug where an upcall can be lost (and to follow Xen's behavior). - Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen events fails, e.g. if the guest has aliased xAPIC IDs. - Extend gfn_to_pfn_cache's mutex to cover (de)activation (in addition to refresh), and drop a now-redundant acquisition of xen_lock (that was protecting the shared_info cache) to fix a deadlock due to recursively acquiring xen_lock.

Merge tag 'kvm-x86-misc-6.9' of https://github.com/kvm-x86/linux into HEAD

2024-03-11T14:24:56+00:00

KVM x86 misc changes for 6.9: - Explicitly initialize a variety of on-stack variables in the emulator that triggered KMSAN false positives (though in fairness in KMSAN, it's comically difficult to see that the uninitialized memory is never truly consumed). - Fix the deubgregs ABI for 32-bit KVM, and clean up code related to reading DR6 and DR7. - Rework the "force immediate exit" code so that vendor code ultimately decides how and when to force the exit. This allows VMX to further optimize handling preemption timer exits, and allows SVM to avoid sending a duplicate IPI (SVM also has a need to force an exit). - Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if vCPU creation ultimately failed, and add WARN to guard against similar bugs. - Provide a dedicated arch hook for checking if a different vCPU was in-kernel (for directed yield), and simplify the logic for checking if the currently loaded vCPU is in-kernel. - Misc cleanups and fixes.

Merge tag 'kvm-x86-generic-6.9' of https://github.com/kvm-x86/linux into HEAD

2024-03-11T14:23:03+00:00

KVM common MMU changes for 6.9: - Harden KVM against underflowing the active mmu_notifier invalidation count, so that "bad" invalidations (usually due to bugs elsehwere in the kernel) are detected earlier and are less likely to hang the kernel. - Fix a benign bug in __kvm_mmu_topup_memory_cache() where the object size and number of objects parameters to kvmalloc_array() were swapped.

Merge tag 'kvm-x86-asyncpf-6.9' of https://github.com/kvm-x86/linux into HEAD

2024-03-11T14:22:41+00:00

KVM async page fault changes for 6.9: - Always flush the async page fault workqueue when a work item is being removed, especially during vCPU destruction, to ensure that there are no workers running in KVM code when all references to KVM-the-module are gone, i.e. to prevent a use-after-free if kvm.ko is unloaded. - Grab a reference to the VM's mm_struct in the async #PF worker itself instead of gifting the worker a reference, e.g. so that there's no need to remember to *conditionally* clean up after the worker.