* [bug report] KVM: arm64: Always invalidate TLB for stage-2 permission faults
@ 2024-02-01 10:17 Dan Carpenter
2024-02-01 17:59 ` Oliver Upton
0 siblings, 1 reply; 2+ messages in thread
From: Dan Carpenter @ 2024-02-01 10:17 UTC (permalink / raw)
To: oliver.upton; +Cc: kvmarm
Hello Oliver Upton,
The patch be097997a273: "KVM: arm64: Always invalidate TLB for
stage-2 permission faults" from Sep 22, 2023 (linux-next), leads to
the following Smatch static checker warning:
arch/arm64/kvm/hyp/nvhe/../pgtable.c:1342 kvm_pgtable_stage2_relax_perms()
error: uninitialized symbol 'level'.
arch/arm64/kvm/hyp/nvhe/../pgtable.c
1319 int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,
1320 enum kvm_pgtable_prot prot)
1321 {
1322 int ret;
1323 s8 level;
1324 kvm_pte_t set = 0, clr = 0;
1325
1326 if (prot & KVM_PTE_LEAF_ATTR_HI_SW)
1327 return -EINVAL;
1328
1329 if (prot & KVM_PGTABLE_PROT_R)
1330 set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R;
1331
1332 if (prot & KVM_PGTABLE_PROT_W)
1333 set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W;
1334
1335 if (prot & KVM_PGTABLE_PROT_X)
1336 clr |= KVM_PTE_LEAF_ATTR_HI_S2_XN;
1337
1338 ret = stage2_update_leaf_attrs(pgt, addr, 1, set, clr, NULL, &level,
1339 KVM_PGTABLE_WALK_HANDLE_FAULT |
1340 KVM_PGTABLE_WALK_SHARED);
1341 if (!ret || ret == -EAGAIN)
--> 1342 kvm_call_hyp(__kvm_tlb_flush_vmid_ipa_nsh, pgt->mmu, addr, level);
^^^^^
level is uninitialized if ret is -EAGAIN
1343 return ret;
1344 }
regards,
dan carpenter
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: [bug report] KVM: arm64: Always invalidate TLB for stage-2 permission faults
2024-02-01 10:17 [bug report] KVM: arm64: Always invalidate TLB for stage-2 permission faults Dan Carpenter
@ 2024-02-01 17:59 ` Oliver Upton
0 siblings, 0 replies; 2+ messages in thread
From: Oliver Upton @ 2024-02-01 17:59 UTC (permalink / raw)
To: Dan Carpenter; +Cc: kvmarm
On Thu, Feb 01, 2024 at 01:17:15PM +0300, Dan Carpenter wrote:
> Hello Oliver Upton,
>
> The patch be097997a273: "KVM: arm64: Always invalidate TLB for
> stage-2 permission faults" from Sep 22, 2023 (linux-next), leads to
> the following Smatch static checker warning:
>
> arch/arm64/kvm/hyp/nvhe/../pgtable.c:1342 kvm_pgtable_stage2_relax_perms()
> error: uninitialized symbol 'level'.
>
> arch/arm64/kvm/hyp/nvhe/../pgtable.c
> 1319 int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,
> 1320 enum kvm_pgtable_prot prot)
> 1321 {
> 1322 int ret;
> 1323 s8 level;
> 1324 kvm_pte_t set = 0, clr = 0;
> 1325
> 1326 if (prot & KVM_PTE_LEAF_ATTR_HI_SW)
> 1327 return -EINVAL;
> 1328
> 1329 if (prot & KVM_PGTABLE_PROT_R)
> 1330 set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R;
> 1331
> 1332 if (prot & KVM_PGTABLE_PROT_W)
> 1333 set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W;
> 1334
> 1335 if (prot & KVM_PGTABLE_PROT_X)
> 1336 clr |= KVM_PTE_LEAF_ATTR_HI_S2_XN;
> 1337
> 1338 ret = stage2_update_leaf_attrs(pgt, addr, 1, set, clr, NULL, &level,
> 1339 KVM_PGTABLE_WALK_HANDLE_FAULT |
> 1340 KVM_PGTABLE_WALK_SHARED);
> 1341 if (!ret || ret == -EAGAIN)
> --> 1342 kvm_call_hyp(__kvm_tlb_flush_vmid_ipa_nsh, pgt->mmu, addr, level);
> ^^^^^
> level is uninitialized if ret is -EAGAIN
Hmm, race detection can happen at any level in the walk and that may not
be a leaf level. We can initialize level to -1 which would provide no
TTL hint for this case.
--
Thanks,
Oliver
^ permalink raw reply [flat|nested] 2+ messages in thread
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2024-02-01 10:17 [bug report] KVM: arm64: Always invalidate TLB for stage-2 permission faults Dan Carpenter
2024-02-01 17:59 ` Oliver Upton
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