It was found that passing an invalid cpu number to pv_vcpu_is_preempted()
might panic the kernel in a VM guest. For example,
[ 2.531077] Oops: 0000 [#1] SMP PTI
:
[ 2.532545] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[ 2.533321] RIP: 0010:__raw_callee_save___kvm_vcpu_is_preempted+0x0/0x20
To guard against this kind of kernel panic, check is added to
pv_vcpu_is_preempted() to make sure that no invalid cpu number will
be used.
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
arch/x86/include/asm/paravirt.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index c25c38a05c1c..4cfb465dcde4 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -671,6 +671,12 @@ static __always_inline void pv_kick(int cpu)
static __always_inline bool pv_vcpu_is_preempted(long cpu)
{
+ /*
+ * Guard against invalid cpu number or the kernel might panic.
+ */
+ if (WARN_ON_ONCE((unsigned long)cpu >= nr_cpu_ids))
+ return false;
+
return PVOP_CALLEE1(bool, lock.vcpu_is_preempted, cpu);
}
--
2.18.1
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