Il 20/02/2014 14:18, walter harms ha scritto:
Am 20.02.2014 14:07, schrieb Paolo Bonzini:
Il 20/02/2014 13:34, Dan Carpenter ha scritto:
This seems like a harmless off by one overflow if "i" is the last
element in the vcpu->arch.cpuid_entries[] array.
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
---
Not tested. I always wonder if it's worth fixing these or if it's worth
reporting them? Either of those seem like a lot of work for something
harmless.
Could it oops if cpuid_nent is INT_MAX? If so, it's not entirely harmless.
In this case I'd rather take the occasion to cleanup the code like this
(compile-tested):
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 9fed5bedaad6..2fd6e7169936 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -656,18 +656,19 @@ out:
static int move_to_next_stateful_cpuid_entry(struct kvm_vcpu *vcpu, int i)
{
struct kvm_cpuid_entry2 *e = &vcpu->arch.cpuid_entries[i];
- int j, nent = vcpu->arch.cpuid_nent;
+ struct kvm_cpuid_entry2 *ej;
+ int j = i, nent = vcpu->arch.cpuid_nent;
e->flags &= ~KVM_CPUID_FLAG_STATE_READ_NEXT;
+
/* when no next entry is found, the current entry[i] is reselected */
- for (j = i + 1; ; j = (j + 1) % nent) {
- struct kvm_cpuid_entry2 *ej = &vcpu->arch.cpuid_entries[j];
- if (ej->function == e->function) {
- ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
- return j;
- }
- }
- return 0; /* silence gcc, even though control never reaches here */
+ do {
+ j = (j + 1) % nent;
+ ej = &vcpu->arch.cpuid_entries[j];
+ } while (ej->function != e->function);
+
+ ej->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
+ return j;
}
/* find an entry with matching function, matching index (if needed), and that
What do you think?
Is there any guaranty that this will not loop forever ?
an if (i==j) return 0; would be on the save side. (I guess that
these was the idea behind the for).
Once i==j you'll get ej->function == e->function and exit.
Paolo
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