linux-kernel - [PATCH 4.19 155/220] reset: Fix potential use-after-free in __of_reset_control

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Message-Id: <20191122100923.863834722@linuxfoundation.org>
Date:   Fri, 22 Nov 2019 11:28:40 +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,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 155/220] reset: Fix potential use-after-free in __of_reset_control_get()

From: Geert Uytterhoeven <geert+renesas@...der.be>

[ Upstream commit b790c8ea5593d6dc3580adfad8e117eeb56af874 ]

Calling of_node_put() decreases the reference count of a device tree
object, and may free some data.

However, the of_phandle_args structure embedding it is passed to
reset_controller_dev.of_xlate() after that, so it may still be accessed.

Move the call to of_node_put() down to fix this.

Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
[p.zabel@...gutronix.de: moved of_node_put after mutex_unlock]
Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/reset/core.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index 225e34c56b94a..d1887c0ed5d3f 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -496,28 +496,29 @@ struct reset_control *__of_reset_control_get(struct device_node *node,
 			break;
 		}
 	}
-	of_node_put(args.np);
 
 	if (!rcdev) {
-		mutex_unlock(&reset_list_mutex);
-		return ERR_PTR(-EPROBE_DEFER);
+		rstc = ERR_PTR(-EPROBE_DEFER);
+		goto out;
 	}
 
 	if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) {
-		mutex_unlock(&reset_list_mutex);
-		return ERR_PTR(-EINVAL);
+		rstc = ERR_PTR(-EINVAL);
+		goto out;
 	}
 
 	rstc_id = rcdev->of_xlate(rcdev, &args);
 	if (rstc_id < 0) {
-		mutex_unlock(&reset_list_mutex);
-		return ERR_PTR(rstc_id);
+		rstc = ERR_PTR(rstc_id);
+		goto out;
 	}
 
 	/* reset_list_mutex also protects the rcdev's reset_control list */
 	rstc = __reset_control_get_internal(rcdev, rstc_id, shared);
 
+out:
 	mutex_unlock(&reset_list_mutex);
+	of_node_put(args.np);
 
 	return rstc;
 }
-- 
2.20.1