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linux/arch/x86/kvm
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Vasiliy Kovalev 57536ff0a6 KVM: x86: Add SRCU protection for reading PDPTRs in __get_sregs2() 
[ Upstream commit 95d848dc7e ]

Add SRCU read-side protection when reading PDPTR registers in
__get_sregs2().

Reading PDPTRs may trigger access to guest memory:
kvm_pdptr_read() -> svm_cache_reg() -> load_pdptrs() ->
kvm_vcpu_read_guest_page() -> kvm_vcpu_gfn_to_memslot()

kvm_vcpu_gfn_to_memslot() dereferences memslots via __kvm_memslots(),
which uses srcu_dereference_check() and requires either kvm->srcu or
kvm->slots_lock to be held. Currently only vcpu->mutex is held,
triggering lockdep warning:

=============================
WARNING: suspicious RCU usage in kvm_vcpu_gfn_to_memslot
6.12.59+ #3 Not tainted

include/linux/kvm_host.h:1062 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz.5.1717/15100:
 #0: ff1100002f4b00b0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x1d5/0x1590

Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0xf0/0x120 lib/dump_stack.c:120
 lockdep_rcu_suspicious+0x1e3/0x270 kernel/locking/lockdep.c:6824
 __kvm_memslots include/linux/kvm_host.h:1062 [inline]
 __kvm_memslots include/linux/kvm_host.h:1059 [inline]
 kvm_vcpu_memslots include/linux/kvm_host.h:1076 [inline]
 kvm_vcpu_gfn_to_memslot+0x518/0x5e0 virt/kvm/kvm_main.c:2617
 kvm_vcpu_read_guest_page+0x27/0x50 virt/kvm/kvm_main.c:3302
 load_pdptrs+0xff/0x4b0 arch/x86/kvm/x86.c:1065
 svm_cache_reg+0x1c9/0x230 arch/x86/kvm/svm/svm.c:1688
 kvm_pdptr_read arch/x86/kvm/kvm_cache_regs.h:141 [inline]
 __get_sregs2 arch/x86/kvm/x86.c:11784 [inline]
 kvm_arch_vcpu_ioctl+0x3e20/0x4aa0 arch/x86/kvm/x86.c:6279
 kvm_vcpu_ioctl+0x856/0x1590 virt/kvm/kvm_main.c:4663
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl fs/ioctl.c:893 [inline]
 __x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xbd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: stable@vger.kernel.org
Fixes: 6dba940352 ("KVM: x86: Introduce KVM_GET_SREGS2 / KVM_SET_SREGS2")
Signed-off-by: Vasiliy Kovalev <kovalev@altlinux.org>
Link: https://patch.msgid.link/20260123222801.646123-1-kovalev@altlinux.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-04 07:21:15 -05:00
..
mmu KVM: x86: Export KVM-internal symbols for sub-modules only 2025-09-30 13:40:02 -04:00
svm KVM: nSVM: Always use vmcb01 in VMLOAD/VMSAVE emulation 2026-03-04 07:21:05 -05:00
vmx KVM: x86: Explicitly configure supported XSS from {svm,vmx}_set_cpu_caps() 2026-02-11 13:41:40 +01:00
.gitignore KVM: x86: use a separate asm-offsets.c file 2022-11-09 12:10:17 -05:00
cpuid.c KVM: x86: Apply runtime updates to current CPUID during KVM_SET_CPUID{,2} 2026-01-02 12:57:21 +01:00
cpuid.h Merge branch 'kvm-tdx-initial' into HEAD 2025-04-07 07:36:33 -04:00
debugfs.c KVM: Get rid of return value from kvm_arch_create_vm_debugfs() 2024-02-23 21:44:58 +00:00
emulate.c - Remove a bunch of asm implementing condition flags testing in KVM's 2025-10-11 11:19:16 -07:00
fpu.h KVM: x86: Move FPU register accessors into fpu.h 2021-06-17 13:09:24 -04:00
hyperv.c KVM: x86: Export KVM-internal symbols for sub-modules only 2025-09-30 13:40:02 -04:00
hyperv.h KVM: x86: Drop superfluous kvm_hv_set_sint() => kvm_hv_synic_set_irq() wrapper 2025-06-20 13:52:43 -07:00
i8254.c Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
i8254.h KVM: x86: Move IRQ mask notifier infrastructure to I/O APIC emulation 2025-06-20 13:52:52 -07:00
i8259.c KVM: x86: Move IRQ mask notifier infrastructure to I/O APIC emulation 2025-06-20 13:52:52 -07:00
ioapic.c arch/x86/kvm/ioapic: Remove license boilerplate with bad FSF address 2025-08-19 11:59:29 -07:00
ioapic.h KVM: x86: Move IRQ mask notifier infrastructure to I/O APIC emulation 2025-06-20 13:52:52 -07:00
irq.c KVM: x86: Export KVM-internal symbols for sub-modules only 2025-09-30 13:40:02 -04:00
irq.h KVM: x86: Move kvm_irq_delivery_to_apic() from irq.c to lapic.c 2025-09-10 12:05:09 -07:00
Kconfig - Remove a bunch of asm implementing condition flags testing in KVM's 2025-10-11 11:19:16 -07:00
kvm-asm-offsets.c KVM: SVM: move MSR_IA32_SPEC_CTRL save/restore to assembly 2022-11-09 12:25:53 -05:00
kvm_cache_regs.h KVM: VMX: Make CR4.CET a guest owned bit 2025-09-23 10:03:09 -07:00
kvm_emulate.h KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O 2025-08-19 10:53:40 -07:00
kvm_onhyperv.c KVM: x86: Export KVM-internal symbols for sub-modules only 2025-09-30 13:40:02 -04:00
kvm_onhyperv.h KVM: x86: Move Hyper-V partition assist page out of Hyper-V emulation context 2023-12-07 09:34:01 -08:00
lapic.c KVM: x86: Fix VM hard lockup after prolonged inactivity with periodic HV timer 2026-01-02 12:57:20 +01:00
lapic.h KVM: x86: Move kvm_intr_is_single_vcpu() to lapic.c 2025-09-30 13:40:02 -04:00
Makefile KVM: x86: Fold irq_comm.c into irq.c 2025-06-20 13:52:52 -07:00
mmu.h KVM: x86/mmu: WARN on attempt to check permissions for Shadow Stack #PF 2025-09-23 09:16:53 -07:00
mtrr.c KVM: x86: drop x86.h include from cpuid.h 2024-11-01 09:22:23 -07:00
pmu.c KVM: x86/pmu: Don't try to get perf capabilities for hybrid CPUs 2025-10-10 14:25:12 -07:00
pmu.h Generic: 2025-10-06 12:37:34 -07:00
reverse_cpuid.h KVM: x86: Advertise support for the immediate form of MSR instructions 2025-08-19 11:59:47 -07:00
smm.c KVM: x86: Export KVM-internal symbols for sub-modules only 2025-09-30 13:40:02 -04:00
smm.h KVM: x86: Save and reload SSP to/from SMRAM 2025-09-23 09:11:22 -07:00
trace.h KVM: x86: Define AMD's #HV, #VC, and #SX exception vectors 2025-09-23 09:29:03 -07:00
tss.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
x86.c KVM: x86: Add SRCU protection for reading PDPTRs in __get_sregs2() 2026-03-04 07:21:15 -05:00
x86.h KVM: x86: Explicitly configure supported XSS from {svm,vmx}_set_cpu_caps() 2026-02-11 13:41:40 +01:00
xen.c KVM: x86/xen: Fix cleanup logic in emulation of Xen schedop poll hypercalls 2025-07-23 23:48:54 +02:00
xen.h KVM: x86: Update Xen TSC leaves during CPUID emulation 2025-02-25 07:09:55 -08:00