Re: [PATCH] KVM: Array access out of bounds

[Paolo Bonzini]

On 10/23/24 14:01, Liu Jing wrote:
In the kvmppc_mmu_book3s_64_xlate function,
r = be64_to_cpu(pteg[i+1]); i used is 16 after the last loop and adding 1 will 
cross the line.
Signed-off-by: Liu Jing <liuj...@cmss.chinamobile.com>

diff --git a/arch/powerpc/kvm/book3s_64_mmu.c b/arch/powerpc/kvm/book3s_64_mmu.c
index 61290282fd9e..75d2b284c4b4 100644
--- a/arch/powerpc/kvm/book3s_64_mmu.c
+++ b/arch/powerpc/kvm/book3s_64_mmu.c
@@ -284,11 +284,16 @@ static int kvmppc_mmu_book3s_64_xlate(struct kvm_vcpu 
*vcpu, gva_t eaddr,
                second = true;
                goto do_second;
        }
+       if (i < 14) {

This should be i <= 14 (not "<").  And in fact, if you get here you must 
have found == true, and therefore i is indeed <= 14.  The code right 
above is this:

        if (!found) {
                if (second)
                        goto no_page_found;
                v_val |= HPTE_V_SECONDARY;
                second = true;
                goto do_second;
        }

and  "found = true" is set just before a break statement.

Paolo

+               r = be64_to_cpu(pteg[i+1]);
+               pp = (r & HPTE_R_PP) | key;
+               if (r & HPTE_R_PP0)
+                       pp |= 8;
+       } else {
+               dprintk("KVM: Index out of bounds!\n");
+               goto no_page_found;
+       }
  
-	r = be64_to_cpu(pteg[i+1]);
-       pp = (r & HPTE_R_PP) | key;
-       if (r & HPTE_R_PP0)
-               pp |= 8;
  
  	gpte->eaddr = eaddr;
        gpte->vpage = kvmppc_mmu_book3s_64_ea_to_vp(vcpu, eaddr, data);