linux-kernel - [PATCH][next] KVM: x86: Fix potential fput on a null source_kvm

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Message-Id: <20210430170303.131924-1-colin.king@canonical.com>
Date:   Fri, 30 Apr 2021 18:03:03 +0100
From:   Colin King <colin.king@...onical.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Nathan Tempelman <natet@...gle.com>, kvm@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] KVM: x86: Fix potential fput on a null source_kvm_file

From: Colin Ian King <colin.king@...onical.com>

The fget can potentially return null, so the fput on the error return
path can cause a null pointer dereference. Fix this by checking for
a null source_kvm_file before doing a fput.

Addresses-Coverity: ("Dereference null return")
Fixes: 54526d1fd593 ("KVM: x86: Support KVM VMs sharing SEV context")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 arch/x86/kvm/svm/sev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 1356ee095cd5..8b11c711a0e4 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1764,7 +1764,8 @@ int svm_vm_copy_asid_from(struct kvm *kvm, unsigned int source_fd)
 e_source_unlock:
 	mutex_unlock(&source_kvm->lock);
 e_source_put:
-	fput(source_kvm_file);
+	if (source_kvm_file)
+		fput(source_kvm_file);
 	return ret;
 }
 
-- 
2.30.2