linux-kernel - [PATCH v2 1/2] KVM: x86: Reduce refcount if single_open() fails in kvm_mmu_rmaps_stat

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Date:   Mon, 17 Oct 2022 11:06:09 +0800
From:   "Hou Wenlong" <houwenlong.hwl@...group.com>
To:     kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Peter Xu <peterx@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/2] KVM: x86: Reduce refcount if single_open() fails in kvm_mmu_rmaps_stat_open()

Refcount is increased before calling single_open() in
kvm_mmu_rmaps_stat_open(), If single_open() fails, refcount should be
restored, otherwise the vm couldn't be destroyed.

Fixes: 3bcd0662d66fd ("KVM: X86: Introduce mmu_rmaps_stat per-vm debugfs file")
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/kvm/debugfs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c
index cfed36aba2f7..e6efd0821c59 100644
--- a/arch/x86/kvm/debugfs.c
+++ b/arch/x86/kvm/debugfs.c
@@ -157,12 +157,17 @@ static int kvm_mmu_rmaps_stat_show(struct seq_file *m, void *v)
 
 static int kvm_mmu_rmaps_stat_open(struct inode *inode, struct file *file)
 {
+	int ret;
 	struct kvm *kvm = inode->i_private;
 
 	if (!kvm_get_kvm_safe(kvm))
 		return -ENOENT;
 
-	return single_open(file, kvm_mmu_rmaps_stat_show, kvm);
+	ret = single_open(file, kvm_mmu_rmaps_stat_show, kvm);
+	if (ret)
+		kvm_put_kvm(kvm);
+
+	return ret;
 }
 
 static int kvm_mmu_rmaps_stat_release(struct inode *inode, struct file *file)
-- 
2.31.1