diff options
authorGreg Kurz <>2020-03-18 18:43:30 +0100
committerMichael Ellerman <>2020-03-20 13:39:10 +1100
commit1d0c32ec3b860a32df593a22bad0d1dbc5546a59 (patch)
parentaf3d0a68698c7e5df8b72267086b23422a3954bb (diff)
KVM: PPC: Fix kernel crash with PR KVM
With PR KVM, shutting down a VM causes the host kernel to crash: [ 314.219284] BUG: Unable to handle kernel data access on read at 0xc00800000176c638 [ 314.219299] Faulting instruction address: 0xc008000000d4ddb0 cpu 0x0: Vector: 300 (Data Access) at [c00000036da077a0] pc: c008000000d4ddb0: kvmppc_mmu_pte_flush_all+0x68/0xd0 [kvm_pr] lr: c008000000d4dd94: kvmppc_mmu_pte_flush_all+0x4c/0xd0 [kvm_pr] sp: c00000036da07a30 msr: 900000010280b033 dar: c00800000176c638 dsisr: 40000000 current = 0xc00000036d4c0000 paca = 0xc000000001a00000 irqmask: 0x03 irq_happened: 0x01 pid = 1992, comm = qemu-system-ppc Linux version 5.6.0-master-gku+ (greg@palmb) (gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)) #17 SMP Wed Mar 18 13:49:29 CET 2020 enter ? for help [c00000036da07ab0] c008000000d4fbe0 kvmppc_mmu_destroy_pr+0x28/0x60 [kvm_pr] [c00000036da07ae0] c0080000009eab8c kvmppc_mmu_destroy+0x34/0x50 [kvm] [c00000036da07b00] c0080000009e50c0 kvm_arch_vcpu_destroy+0x108/0x140 [kvm] [c00000036da07b30] c0080000009d1b50 kvm_vcpu_destroy+0x28/0x80 [kvm] [c00000036da07b60] c0080000009e4434 kvm_arch_destroy_vm+0xbc/0x190 [kvm] [c00000036da07ba0] c0080000009d9c2c kvm_put_kvm+0x1d4/0x3f0 [kvm] [c00000036da07c00] c0080000009da760 kvm_vm_release+0x38/0x60 [kvm] [c00000036da07c30] c000000000420be0 __fput+0xe0/0x310 [c00000036da07c90] c0000000001747a0 task_work_run+0x150/0x1c0 [c00000036da07cf0] c00000000014896c do_exit+0x44c/0xd00 [c00000036da07dc0] c0000000001492f4 do_group_exit+0x64/0xd0 [c00000036da07e00] c000000000149384 sys_exit_group+0x24/0x30 [c00000036da07e20] c00000000000b9d0 system_call+0x5c/0x68 This is caused by a use-after-free in kvmppc_mmu_pte_flush_all() which dereferences vcpu->arch.book3s which was previously freed by kvmppc_core_vcpu_free_pr(). This happens because kvmppc_mmu_destroy() is called after kvmppc_core_vcpu_free() since commit ff030fdf5573 ("KVM: PPC: Move kvm_vcpu_init() invocation to common code"). The kvmppc_mmu_destroy() helper calls one of the following depending on the KVM backend: - kvmppc_mmu_destroy_hv() which does nothing (Book3s HV) - kvmppc_mmu_destroy_pr() which undoes the effects of kvmppc_mmu_init() (Book3s PR 32-bit) - kvmppc_mmu_destroy_pr() which undoes the effects of kvmppc_mmu_init() (Book3s PR 64-bit) - kvmppc_mmu_destroy_e500() which does nothing (BookE e500/e500mc) It turns out that this is only relevant to PR KVM actually. And both 32 and 64 backends need vcpu->arch.book3s to be valid when calling kvmppc_mmu_destroy_pr(). So instead of calling kvmppc_mmu_destroy() from kvm_arch_vcpu_destroy(), call kvmppc_mmu_destroy_pr() at the beginning of kvmppc_core_vcpu_free_pr(). This is consistent with kvmppc_mmu_init() being the last call in kvmppc_core_vcpu_create_pr(). For the same reason, if kvmppc_core_vcpu_create_pr() returns an error then this means that kvmppc_mmu_init() was either not called or failed, in which case kvmppc_mmu_destroy() should not be called. Drop the line in the error path of kvm_arch_vcpu_create(). Fixes: ff030fdf5573 ("KVM: PPC: Move kvm_vcpu_init() invocation to common code") Signed-off-by: Greg Kurz <> Reviewed-by: Sean Christopherson <> Signed-off-by: Michael Ellerman <> Link:
2 files changed, 1 insertions, 2 deletions
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 729a0f12a752..db3a87319642 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -1817,6 +1817,7 @@ static void kvmppc_core_vcpu_free_pr(struct kvm_vcpu *vcpu)
struct kvmppc_vcpu_book3s *vcpu_book3s = to_book3s(vcpu);
+ kvmppc_mmu_destroy_pr(vcpu);
free_page((unsigned long)vcpu->arch.shared & PAGE_MASK);
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 1af96fb5dc6f..302e9dccdd6d 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -759,7 +759,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
return 0;
- kvmppc_mmu_destroy(vcpu);
return err;
@@ -792,7 +791,6 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
- kvmppc_mmu_destroy(vcpu);