From: Coleman Dietsch <dietschc@csp.edu>
To: dietschc@csp.edu, kvm@vger.kernel.org
Cc: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, skhan@linuxfoundation.org,
Pavel Skripkin <paskripkin@gmail.com>,
linux-kernel-mentees@lists.linuxfoundation.org
Subject: [PATCH v3 0/2] KVM: x86/xen: Prevent Xen timer init when running
Date: Mon, 8 Aug 2022 14:02:10 -0500 [thread overview]
Message-ID: <20220808190211.323827-1-dietschc@csp.edu> (raw)
The following issue was discovered by syzbot:
WARNING: ODEBUG bug in kvm_xen_vcpu_set_attr.
When running the syzbot reproducer code, the following crash dump occurs:
ODEBUG: init active (active state 0)
object type: hrtimer hint: xen_timer_callbac0
RIP: 0010:debug_print_object+0x16e/0x250 lib/debugobjects.c:502
Call Trace:
__debug_object_init
debug_hrtimer_init
debug_init
hrtimer_init
kvm_xen_init_timer
kvm_xen_vcpu_set_attr
kvm_arch_vcpu_ioctl
kvm_vcpu_ioctl
vfs_ioctl
The ODEBUG bug crash appears to be happening when vcpu->arch.xen.timer is
already set and kvm_xen_init_timer() is called, which appears to be the
result of two separate issues.
The first issue is that kvm_xen_init_timer() is run "every"
KVM_XEN_VCPU_ATTR_TYPE_TIMER. This is addressed in patch 1.
The second issue is that the stop xen timer code should be run before
changing the IRQ vector. This is addressed in patch 2 with some cleanup.
version 3 changes
-removed ambiguous comment
-updated another comment to be more descriptive
-continue cleaning up changelogs
version 2 changes (mostly feedback from Sean Christopherson)
-split patch into 2 patches
-fix changelogs to be more descriptive
-fix formatting issues
-add check for existing xen timer before trying to initialize another one
-removed conditional for kvm_xen_stop_timer() so that it always runs
-ensure that xen timer is stopped before changing IRQ vector
-streamlined switch case KVM_XEN_VCPU_ATTR_TYPE_TIMER a bit
Coleman Dietsch (2):
KVM: x86/xen: Initialize Xen timer only once
KVM: x86/xen: Stop Xen timer before changing IRQ
arch/x86/kvm/xen.c | 31 ++++++++++++++++---------------
1 file changed, 16 insertions(+), 15 deletions(-)
--
2.34.1
next reply other threads:[~2022-08-08 19:03 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-08 19:02 Coleman Dietsch [this message]
2022-08-09 0:36 ` Sean Christopherson
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