linux-kernel - [PATCH 5.15 621/917] powerpc: fix unbalanced node refcount in check_kvm

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Message-Id: <20211115165449.853472793@linuxfoundation.org>
Date:   Mon, 15 Nov 2021 18:01:56 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nathan Lynch <nathanl@...ux.ibm.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Tyrel Datwyler <tyreld@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 621/917] powerpc: fix unbalanced node refcount in check_kvm_guest()

From: Nathan Lynch <nathanl@...ux.ibm.com>

[ Upstream commit 56537faf8821e361d739fc5ff58c9c40f54a1d4c ]

When check_kvm_guest() succeeds in looking up a /hypervisor OF node, it
returns without performing a matching put for the lookup, leaving the
node's reference count elevated.

Add the necessary call to of_node_put(), rearranging the code slightly to
avoid repetition or goto.

Fixes: 107c55005fbd ("powerpc/pseries: Add KVM guest doorbell restrictions")
Signed-off-by: Nathan Lynch <nathanl@...ux.ibm.com>
Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Reviewed-by: Tyrel Datwyler <tyreld@...ux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20210928124550.132020-1-nathanl@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/kernel/firmware.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/firmware.c b/arch/powerpc/kernel/firmware.c
index c7022c41cc314..20328f72f9f2b 100644
--- a/arch/powerpc/kernel/firmware.c
+++ b/arch/powerpc/kernel/firmware.c
@@ -31,11 +31,10 @@ int __init check_kvm_guest(void)
 	if (!hyper_node)
 		return 0;
 
-	if (!of_device_is_compatible(hyper_node, "linux,kvm"))
-		return 0;
-
-	static_branch_enable(&kvm_guest);
+	if (of_device_is_compatible(hyper_node, "linux,kvm"))
+		static_branch_enable(&kvm_guest);
 
+	of_node_put(hyper_node);
 	return 0;
 }
 core_initcall(check_kvm_guest); // before kvm_guest_init()
-- 
2.33.0