[syzbot ci] Re: KVM: x86: Introduce memory protection attributes

[syzbot ci]

syzbot ci has tested the following series

[v4] KVM: x86: Introduce memory protection attributes
https://lore.kernel.org/all/20261102174130.8779-1-pbonzini@xxxxxxxxxx
* [PATCH 01/45] KVM: nVMX/nSVM: check unconditionally whether CR3 is valid
* [PATCH 02/45] KVM: x86/hyperv: do not overwrite hc->ingpa for SIGNAL_EVENT hypercall
* [PATCH 03/45] KVM: x86: apply nGPA->GPA translation to KVM_HC_CLOCK_PAIRING
* [PATCH 04/45] KVM: x86/emulate: Check TSS busy-bit writes during task switches
* [PATCH 05/45] KVM: loongarch: do full validity check on the gfn-to-hva cache
* [PATCH 06/45] KVM: selftests: Test address translation for Hyper-V direct L2 hypercalls
* [PATCH 07/45] KVM: selftests: Take into account mixed memory fault flags
* [PATCH 08/45] selftests: kvm: drop TEST_ASSERT_SUPPORTED_ATTRIBUTES
* [PATCH 09/45] KVM: Define and communicate KVM_EXIT_MEMORY_FAULT RWX flags to userspace
* [PATCH 10/45] KVM: x86: Introduce memory fault on invalid hypercalls reads/writes
* [PATCH 11/45] KVM: selftests: test hypercall memory fault exits
* [PATCH 12/45] KVM: x86/mmu: intersect writability from __kvm_faultin_pfn with fault->map_writable
* [PATCH 13/45] KVM: x86/mmu: Extend map_writable to a full ACC_* mask
* [PATCH 14/45] KVM: x86/mmu: Init memslot hugepage information for non-private_mem VMs too
* [PATCH 15/45] KVM: VMX: return error from kvm_set_cr*
* [PATCH 16/45] KVM: adjust for presence of more than one attribute
* [PATCH 17/45] KVM: Introduce NR/NW/NX memory attributes
* [PATCH 18/45] KVM: Include memory protections in result of gfn->hva conversion
* [PATCH 19/45] KVM: Introduce kvm_fetch_guest_page() and use it for x86
* [PATCH 20/45] KVM: Take memory protections into account for memory read/write/fetch
* [PATCH 21/45] KVM: Take memory protections into account for __kvm_vcpu_map
* [PATCH 22/45] KVM: Encapsulate memattrs array into anonymous struct
* [PATCH 23/45] KVM: Introduce kvm_check_gen()/kvm_memslots_check_gen()
* [PATCH 24/45] KVM: Introduce a generation number for memory attributes
* [PATCH 25/45] KVM: Take memory protections into account for accesses with cached gfn->hva
* [PATCH 26/45] KVM: pfncache: Fail to refresh if it contains memory protections
* [PATCH 27/45] KVM: x86/mmu: Do not prefetch sptes on gfns backed by memory attributes
* [PATCH 28/45] KVM: x86/mmu: Take memory protection attributes into account during faults
* [PATCH 29/45] KVM: x86/emulate: change return value of emulator_io_permitted to int
* [PATCH 30/45] KVM: x86/emulate: Propagate memory faults to userspace
* [PATCH 31/45] KVM: x86: "Handle" failed decode when skipping instructions
* [PATCH 32/45] KVM: vmx/sgx: make return value of sgx_gva_to_gpa consistent with its callers
* [PATCH 33/45] KVM: x86: Allow page fault fixup to return errors
* [PATCH 34/45] KVM: x86/mmu: Adjust gva_to_gpa to allow returning an error
* [PATCH 35/45] KVM: x86/mmu: Propagate errors from nested GPA translation
* [PATCH 36/45] KVM: x86: Propagate memory faults through load_pdptrs()
* [PATCH 37/45] KVM: x86/mmu: Issue memory fault exit if walk failed due to memory attribute
* [PATCH 38/45] KVM: x86: mark VM as dead after KVM_SET_SREGS fails to load PDPTRs
* [PATCH 39/45] KVM: VMX: mark VM dead on shadow VMCS or eVMCS access failures
* [PATCH 40/45] KVM: let kvm_arch_post_set_memory_attributes drop mmu_lock
* [PATCH 41/45] KVM: x86/mmu: Obsolete all roots if memattr contains gPTEs
* [PATCH 42/45] KVM: x86: selftests: Introduce memory protection attributes test
* [PATCH 43/45] KVM: x86: selftests: Introduce memory attributes PTE test
* [PATCH 44/45] KVM: x86: selftests: Introduce memory attributes side-channel tests
* [PATCH 45/45] KVM: x86: split out parts of load_pdptrs

and found the following issue:
WARNING: suspicious RCU usage in __kvm_gpc_refresh

Full report is available here:
https://ci.syzbot.org/series/beb5d6f5-3128-404c-9de5-537fb4326658

***

WARNING: suspicious RCU usage in __kvm_gpc_refresh

tree:      kvm-next
URL:       https://kernel.googlesource.com/pub/scm/virt/kvm/kvm/
base:      d21eef2084a9af87ac2a783bc7c2b175ba114e4e
arch:      amd64
compiler:  Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
config:    https://ci.syzbot.org/builds/1748209f-578f-45cd-8bb4-6f6392d79a88/config
syz repro: https://ci.syzbot.org/findings/d02cf2a1-ed84-4f69-ac5f-29b2075b5e1f/syz_repro

=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
./include/linux/kvm_host.h:2636 Suspicious memory attribute generation usage
!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
locks held by syz.1.189/6607: 2, last CPU#0:
 #0: ffff8881bf19dc38 (&gpc->refresh_lock){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:253 [inline]
 #0: ffff8881bf19dc38 (&gpc->refresh_lock){+.+.}-{4:4}, at: __kvm_gpc_activate+0x91/0x3b0 virt/kvm/pfncache.c:417
 #1: ffff8881bf19dbb0 (&gpc->lock){....}-{3:3}, at: __kvm_gpc_refresh+0x1af/0x1830 virt/kvm/pfncache.c:272

stack backtrace:
CPU: 0 UID: 0 PID: 6607 Comm: syz.1.189 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 lockdep_rcu_suspicious+0x140/0x1d0 kernel/locking/lockdep.c:6972
 kvm_mem_attributes_generation include/linux/kvm_host.h:2634 [inline]
 __kvm_gpc_refresh+0x1657/0x1830 virt/kvm/pfncache.c:306
 __kvm_gpc_activate+0x289/0x3b0 virt/kvm/pfncache.c:436
 kvm_set_msr_common+0x2dab/0x4320 arch/x86/kvm/msrs.c:-1
 vmx_set_msr+0x15b3/0x27f0 arch/x86/kvm/vmx/vmx.c:2632
 __kvm_set_msr+0x60c/0xab0 arch/x86/kvm/msrs.c:806
 _kvm_set_msr arch/x86/kvm/msrs.c:812 [inline]
 kvm_do_msr_access arch/x86/kvm/msrs.c:549 [inline]
 kvm_set_msr_ignored_check+0x2a/0x390 arch/x86/kvm/msrs.c:818
 nested_vmx_load_msr+0x245/0x4d0 arch/x86/kvm/vmx/nested.c:1126
 load_vmcs12_host_state+0x10ca/0x1e20 arch/x86/kvm/vmx/nested.c:4935
 __nested_vmx_vmexit+0x1a12/0x2c90 arch/x86/kvm/vmx/nested.c:5203
 nested_vmx_vmexit arch/x86/kvm/vmx/nested.h:46 [inline]
 vmx_leave_nested arch/x86/kvm/vmx/nested.c:6898 [inline]
 nested_vmx_free_vcpu+0x8e/0xd0 arch/x86/kvm/vmx/nested.c:389
 vmx_vcpu_free+0x109/0x3e0 arch/x86/kvm/vmx/vmx.c:7536
 kvm_arch_vcpu_destroy+0x154/0x380 arch/x86/kvm/x86.c:9627
 kvm_vcpu_destroy virt/kvm/kvm_main.c:477 [inline]
 kvm_destroy_vcpus+0x123/0x380 virt/kvm/kvm_main.c:497
 kvm_arch_destroy_vm+0xf6/0x1d0 arch/x86/kvm/x86.c:10198
 kvm_destroy_vm virt/kvm/kvm_main.c:1314 [inline]
 kvm_put_kvm+0x772/0xb50 virt/kvm/kvm_main.c:1351
 kvm_vm_release+0x6b/0x80 virt/kvm/kvm_main.c:1376
 __fput+0x40d/0xa50 fs/file_table.c:512
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x204/0x770 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:343 [inline]
 do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe8f039f559
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff5710adc8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fe8f0627da0 RCX: 00007fe8f039f559
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fe8f0627da0 R08: 00007fe8f0626038 R09: 0000000000000000
R10: 000000000003fd98 R11: 0000000000000246 R12: 00000000000213f0
R13: 00007fe8f062609c R14: 000000000002118b R15: 00007fe8f0626090
 </TASK>


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
  Tested-by: syzbot@xxxxxxxxxxxxxxxxxxxxxxxxx

---
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