linux-kernel - [PATCH v2 1/4] powerpc/kvm/book3s: Fixes possible 'use after release' of kvm

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Date:   Thu,  7 Nov 2019 14:02:55 -0300
From:   Leonardo Bras <leonardo@...ux.ibm.com>
To:     kvm-ppc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Cc:     Leonardo Bras <leonardo@...ux.ibm.com>,
        Paul Mackerras <paulus@...abs.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH v2 1/4] powerpc/kvm/book3s: Fixes possible 'use after release' of kvm

Fixes a possible 'use after free' of kvm variable in
kvm_vm_ioctl_create_spapr_tce, where it does a mutex_unlock(&kvm->lock)
after a kvm_put_kvm(kvm).

Signed-off-by: Leonardo Bras <leonardo@...ux.ibm.com>
---
 arch/powerpc/kvm/book3s_64_vio.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
index 5834db0a54c6..a402ead833b6 100644
--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -316,14 +316,13 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
 
 	if (ret >= 0)
 		list_add_rcu(&stt->list, &kvm->arch.spapr_tce_tables);
-	else
-		kvm_put_kvm(kvm);
 
 	mutex_unlock(&kvm->lock);
 
 	if (ret >= 0)
 		return ret;
 
+	kvm_put_kvm(kvm);
 	kfree(stt);
  fail_acct:
 	account_locked_vm(current->mm, kvmppc_stt_pages(npages), false);
-- 
2.23.0