linux-kernel - [PATCH v2 4/9] of/irq: Fix device node refcount leakage in API of_irq_parse

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Message-Id: <20250209-of_irq_fix-v2-4-93e3a2659aa7@quicinc.com>
Date: Sun, 09 Feb 2025 20:58:57 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Bjorn Helgaas <bhelgaas@...gle.com>, Marc Zyngier <maz@...nel.org>, 
 Stefan Wiehler <stefan.wiehler@...ia.com>, Tony Lindgren <tony@...mide.com>, 
 Thierry Reding <thierry.reding@...il.com>, 
 Benjamin Herrenschmidt <benh@...nel.crashing.org>, 
 Julia Lawall <Julia.Lawall@...6.fr>
Cc: Zijun Hu <zijun_hu@...oud.com>, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Zijun Hu <quic_zijuhu@...cinc.com>, 
 stable@...r.kernel.org
Subject: [PATCH v2 4/9] of/irq: Fix device node refcount leakage in API
 of_irq_parse_raw()

From: Zijun Hu <quic_zijuhu@...cinc.com>

if the node @out_irq->np got by of_irq_parse_raw() is a combo node which
consists of both controller and nexus, namely, of_irq_parse_raw() returns
due to condition (@ipar == @newpar), then the node's refcount was increased
twice, hence causes refcount leakage.

Fix by putting @out_irq->np refcount before returning due to the condition.
Also add comments about refcount of node @out_irq->np got by the API.

Fixes: 041284181226 ("of/irq: Allow matching of an interrupt-map local to an interrupt controller")
Cc: stable@...r.kernel.org
Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
---
 drivers/of/irq.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/of/irq.c b/drivers/of/irq.c
index d88719c316a3931502c34a65b2db8921f7528d99..c41b2533d86d8eceabe8f2e43842af33f22febff 100644
--- a/drivers/of/irq.c
+++ b/drivers/of/irq.c
@@ -165,6 +165,8 @@ const __be32 *of_irq_parse_imap_parent(const __be32 *imap, int len, struct of_ph
  * the specifier for each map, and then returns the translated map.
  *
  * Return: 0 on success and a negative number on error
+ *
+ * Note: refcount of node @out_irq->np is increased by 1 on success.
  */
 int of_irq_parse_raw(const __be32 *addr, struct of_phandle_args *out_irq)
 {
@@ -310,6 +312,12 @@ int of_irq_parse_raw(const __be32 *addr, struct of_phandle_args *out_irq)
 		addrsize = (imap - match_array) - intsize;
 
 		if (ipar == newpar) {
+			/*
+			 * Has got @ipar's refcount, but the refcount was
+			 * got again by of_irq_parse_imap_parent() via its
+			 * alias @newpair.
+			 */
+			of_node_put(ipar);
 			pr_debug("%pOF interrupt-map entry to self\n", ipar);
 			return 0;
 		}

-- 
2.34.1