From: Sean Christopherson <seanjc@google.com>
To: syzbot ci <syzbot+ci6c27aad5db86e5b9@syzkaller.appspotmail.com>
Cc: dwmw2@infradead.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, paul@xen.org, pbonzini@redhat.com,
syzbot@syzkaller.appspotmail.com, vkuznets@redhat.com,
syzbot@lists.linux.dev, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot ci] Re: KVM: x86/hyperv: Fix racy usage of vcpu->arch.hyperv
Date: Fri, 26 Jun 2026 06:24:55 -0700 [thread overview]
Message-ID: <aj59p5e2aa1ir1_O@google.com> (raw)
In-Reply-To: <6a3e24ff.bd346d9a.250aae.0008.GAE@google.com>
On Fri, Jun 26, 2026, syzbot ci wrote:
> ------------[ cut here ]------------
> debug_locks && !(lock_is_held(&(&vcpu->mutex)->dep_map) || vcpu->vcpu_idx < 0 || !refcount_read(&vcpu->kvm->users_count))
> WARNING: ./include/linux/kvm_host.h:996 at kvm_lockdep_assert_vcpu_is_locked_or_unreachable include/linux/kvm_host.h:994 [inline], CPU#1: syz.1.34/5967
> WARNING: ./include/linux/kvm_host.h:996 at to_hv_vcpu arch/x86/kvm/hyperv.h:79 [inline], CPU#1: syz.1.34/5967
> WARNING: ./include/linux/kvm_host.h:996 at kvm_hv_vcpu_uninit+0x198/0x210 arch/x86/kvm/hyperv.c:906, CPU#1: syz.1.34/5967
> Modules linked in:
> CPU: 1 UID: 0 PID: 5967 Comm: syz.1.34 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
> RIP: 0010:kvm_lockdep_assert_vcpu_is_locked_or_unreachable include/linux/kvm_host.h:994 [inline]
> RIP: 0010:to_hv_vcpu arch/x86/kvm/hyperv.h:79 [inline]
> RIP: 0010:kvm_hv_vcpu_uninit+0x198/0x210 arch/x86/kvm/hyperv.c:906
> Code: 48 89 df e8 0a 55 d8 00 48 c7 03 00 00 00 00 eb 05 e8 5c 16 6d 00 5b 41 5c 41 5e 41 5f 5d e9 ff 16 4d 0a cc e8 49 16 6d 00 90 <0f> 0b 90 e9 65 ff ff ff 48 c7 c1 e0 bb 2f 90 80 e1 07 80 c1 03 38
> RSP: 0018:ffffc9000390f960 EFLAGS: 00010293
> RAX: ffffffff8158e9e7 RBX: ffff8881bc192880 RCX: ffff88816ac70000
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
> RBP: 0000000000000001 R08: ffff888101fa1743 R09: 1ffff110203f42e8
> R10: dffffc0000000000 R11: ffffed10203f42e9 R12: 0000000000000000
> R13: 00000000fffffff8 R14: ffff888101fa1740 R15: dffffc0000000000
> FS: 00007f47c1e886c0(0000) GS:ffff8882a92b6000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000200000c64000 CR3: 000000016a5e7000 CR4: 0000000000352ef0
> Call Trace:
> <TASK>
> kvm_arch_vcpu_destroy+0x1a9/0x380 arch/x86/kvm/x86.c:9413
> kvm_vm_ioctl_create_vcpu+0x615/0x990 virt/kvm/kvm_main.c:4269
This is the same thing Sashiko pointed out; I completely botched the cleanup if
vCPU creation fails.
next prev parent reply other threads:[~2026-06-26 13:24 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-25 22:36 [PATCH v3 00/10] KVM: x86/hyperv: Fix racy usage of vcpu->arch.hyperv Sean Christopherson
2026-06-25 22:36 ` [PATCH v3 01/10] KVM: x86/hyperv: Get target FIFO in hv_tlb_flush_enqueue(), not caller Sean Christopherson
2026-06-25 22:36 ` [PATCH v3 02/10] KVM: x86/hyperv: Check for NULL vCPU Hyper-V object in kvm_hv_get_tlb_flush_fifo() Sean Christopherson
2026-06-25 22:36 ` [PATCH v3 03/10] KVM: x86/hyperv: Ensure vCPU's Hyper-V object is initialized on cross-vCPU accesses Sean Christopherson
2026-06-25 22:36 ` [PATCH v3 04/10] KVM: x86/xen: Punt singleshot timer hcalls to userspace if Xen vCPU ID isn't set Sean Christopherson
2026-06-25 22:50 ` sashiko-bot
2026-06-26 8:05 ` David Woodhouse
2026-06-26 14:27 ` Sean Christopherson
2026-06-26 15:19 ` David Woodhouse
2026-06-25 22:36 ` [PATCH v3 05/10] KVM: x86/xen: Consolidate checks on Xen vCPU ID for singleshot timer hypercalls Sean Christopherson
2026-06-25 22:43 ` sashiko-bot
2026-06-25 23:30 ` Sean Christopherson
2026-06-26 8:11 ` David Woodhouse
2026-06-26 14:19 ` Sean Christopherson
2026-06-26 15:32 ` David Woodhouse
2026-06-26 18:12 ` Sean Christopherson
2026-06-25 22:36 ` [PATCH v3 06/10] KVM: Initialize a vCPU's index to '-1' while it's being created Sean Christopherson
2026-06-25 22:57 ` sashiko-bot
2026-06-25 23:31 ` Sean Christopherson
2026-06-25 22:36 ` [PATCH v3 07/10] KVM: Move nVMX's lockdep logic for vcpu->mutex to a common helper Sean Christopherson
2026-06-25 22:36 ` [PATCH v3 08/10] KVM: x86: Treat a vCPU as unreachable if its index is invalid Sean Christopherson
2026-06-25 22:50 ` sashiko-bot
2026-06-25 22:36 ` [PATCH v3 09/10] KVM: x86/hyperv: Assert vCPU's mutex is held in to_hv_vcpu() Sean Christopherson
2026-06-25 22:50 ` sashiko-bot
2026-06-25 22:36 ` [PATCH v3 10/10] KVM: x86/hyperv: Use {READ,WRITE}_ONCE for cross-task synic->active accesses Sean Christopherson
2026-06-26 7:06 ` [syzbot ci] Re: KVM: x86/hyperv: Fix racy usage of vcpu->arch.hyperv syzbot ci
2026-06-26 13:24 ` Sean Christopherson [this message]
-- strict thread matches above, loose matches on Subject: below --
2026-06-12 23:06 [PATCH v2 0/8] " Sean Christopherson
2026-06-13 20:38 ` [syzbot ci] " syzbot ci
2026-06-15 14:28 ` Sean Christopherson
2026-04-23 14:08 [PATCH 0/5] " Sean Christopherson
2026-04-23 20:52 ` [syzbot ci] " syzbot ci
2026-04-23 21:40 ` Sean Christopherson
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