linux-kernel - [PATCH 5.15 190/196] i2c: qcom-cci: dont put a device tree node before i2c_add

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Date:   Mon, 21 Feb 2022 09:50:22 +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,
        Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Wolfram Sang <wsa@...nel.org>
Subject: [PATCH 5.15 190/196] i2c: qcom-cci: dont put a device tree node before i2c_add_adapter()

From: Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>

commit 02a4a69667a2ad32f3b52ca906f19628fbdd8a01 upstream.

There is a minor chance for a race, if a pointer to an i2c-bus subnode
is stored and then reused after releasing its reference, and it would
be sufficient to get one more reference under a loop over children
subnodes.

Fixes: e517526195de ("i2c: Add Qualcomm CCI I2C driver")
Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>
Reviewed-by: Robert Foss <robert.foss@...aro.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Signed-off-by: Wolfram Sang <wsa@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/i2c/busses/i2c-qcom-cci.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

--- a/drivers/i2c/busses/i2c-qcom-cci.c
+++ b/drivers/i2c/busses/i2c-qcom-cci.c
@@ -558,7 +558,7 @@ static int cci_probe(struct platform_dev
 		cci->master[idx].adap.quirks = &cci->data->quirks;
 		cci->master[idx].adap.algo = &cci_algo;
 		cci->master[idx].adap.dev.parent = dev;
-		cci->master[idx].adap.dev.of_node = child;
+		cci->master[idx].adap.dev.of_node = of_node_get(child);
 		cci->master[idx].master = idx;
 		cci->master[idx].cci = cci;
 
@@ -643,8 +643,10 @@ static int cci_probe(struct platform_dev
 			continue;
 
 		ret = i2c_add_adapter(&cci->master[i].adap);
-		if (ret < 0)
+		if (ret < 0) {
+			of_node_put(cci->master[i].adap.dev.of_node);
 			goto error_i2c;
+		}
 	}
 
 	pm_runtime_set_autosuspend_delay(dev, MSEC_PER_SEC);
@@ -656,8 +658,10 @@ static int cci_probe(struct platform_dev
 
 error_i2c:
 	for (--i ; i >= 0; i--) {
-		if (cci->master[i].cci)
+		if (cci->master[i].cci) {
 			i2c_del_adapter(&cci->master[i].adap);
+			of_node_put(cci->master[i].adap.dev.of_node);
+		}
 	}
 error:
 	disable_irq(cci->irq);
@@ -673,8 +677,10 @@ static int cci_remove(struct platform_de
 	int i;
 
 	for (i = 0; i < cci->data->num_masters; i++) {
-		if (cci->master[i].cci)
+		if (cci->master[i].cci) {
 			i2c_del_adapter(&cci->master[i].adap);
+			of_node_put(cci->master[i].adap.dev.of_node);
+		}
 		cci_halt(cci, i);
 	}