KVM: PPC: Book3S HV: fix incorrect NULL check on list iterator

The bug is here:
	if (!p)
                return ret;

The list iterator value 'p' will *always* be set and non-NULL by
list_for_each_entry(), so it is incorrect to assume that the iterator
value will be NULL if the list is empty or no element is found.

To fix the bug, Use a new value 'iter' as the list iterator, while use
the old value 'p' as a dedicated variable to point to the found element.

Fixes: 7d57ac025eeb ("KVM: PPC: Book3S HV: In H_SVM_INIT_DONE, migrate remaining normal-GFNs to secure-GFNs")
Cc: stable@vger.kernel.org # v5.9+
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220414062103.8153-1-xiam0nd.tong@gmail.com

diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
index 45c993dd05f5ef87b52d256165c3a6b7e86e8284..36f2314c58e5f8d5755860907b02d1e8c190fdb8 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -361,13 +361,15 @@ static bool kvmppc_gfn_is_uvmem_pfn(unsigned long gfn, struct kvm *kvm,
 static bool kvmppc_next_nontransitioned_gfn(const struct kvm_memory_slot *memslot,
                struct kvm *kvm, unsigned long *gfn)
 {
-       struct kvmppc_uvmem_slot *p;
+       struct kvmppc_uvmem_slot *p = NULL, *iter;
        bool ret = false;
        unsigned long i;
 
-       list_for_each_entry(p, &kvm->arch.uvmem_pfns, list)
-               if (*gfn >= p->base_pfn && *gfn < p->base_pfn + p->nr_pfns)
+       list_for_each_entry(iter, &kvm->arch.uvmem_pfns, list)
+               if (*gfn >= iter->base_pfn && *gfn < iter->base_pfn + iter->nr_pfns) {
+                       p = iter;
                        break;
+               }
        if (!p)
                return ret;
        /*