linux-kernel - [PATCH AUTOSEL 4.14 084/115] reset: Fix potential use-after-free in __of_reset_control

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Date:   Tue, 12 Nov 2019 20:55:51 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.14 084/115] 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 da4292e9de978..72b96b5c75a8f 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -466,28 +466,29 @@ 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