linux-kernel - [PATCH] reset: Fix potential use-after-free in __of_reset_control

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Date:   Mon,  8 Oct 2018 13:14:35 +0200
From:   Geert Uytterhoeven <geert+renesas@...der.be>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH] reset: Fix potential use-after-free in __of_reset_control_get()

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>
---
 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 225e34c56b94a2e3..bc9df10d31b4bae1 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -496,27 +496,28 @@ 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:
+	of_node_put(args.np);
 	mutex_unlock(&reset_list_mutex);
 
 	return rstc;
-- 
2.17.1