[PATCH 2/2] wifi: carl9170: Revert "carl9170: devres-ing hwrng_register usage"

[Dmitry Torokhov]

This reverts commit 23de0fa0d2a05ff71c7bc8df9d12c9f23be83f13.

carl9170_register() is invoked asynchronously from the
request_firmware_nowait() callback after carl9170_usb_probe() has
already returned, and carl9170_usb_disconnect() calls
carl9170_unregister() followed immediately by carl9170_free(), which
frees struct ar9170 (including struct hwrng ar->rng.rng and
ar->rng.name).

Registering the hardware random number generator via
devm_hwrng_register(&ar->udev->dev, &ar->rng.rng) ties its
unregistration to the parent struct usb_device rather than the driver
lifecycle. Furthermore, if carl9170_rng_get() fails at the end of
carl9170_register_hwrng(), or when the interface is disconnected and
carl9170_free() frees struct ar9170 before devres_release_all() runs,
the embedded struct hwrng remains registered on the global rng_list in
freed memory, causing a use-after-free.

Fixes: 23de0fa0d2a0 ("carl9170: devres-ing hwrng_register usage")
Cc: stable@xxxxxxxxxxxxxxx
Assisted-by: LLM
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
---
 drivers/net/wireless/ath/carl9170/carl9170.h |  1 +
 drivers/net/wireless/ath/carl9170/main.c     | 29 +++++++++++++++++++++++++---
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/carl9170/carl9170.h b/drivers/net/wireless/ath/carl9170/carl9170.h
index e66e3e2ae952..03a94a5a209b 100644
--- a/drivers/net/wireless/ath/carl9170/carl9170.h
+++ b/drivers/net/wireless/ath/carl9170/carl9170.h
@@ -454,6 +454,7 @@ struct ar9170 {
 # define CARL9170_HWRNG_CACHE_SIZE	CARL9170_MAX_CMD_PAYLOAD_LEN
 	struct {
 		struct hwrng rng;
+		bool initialized;
 		char name[30 + 1];
 		u16 cache[CARL9170_HWRNG_CACHE_SIZE / sizeof(u16)];
 		unsigned int cache_idx;
diff --git a/drivers/net/wireless/ath/carl9170/main.c b/drivers/net/wireless/ath/carl9170/main.c
index 702b6d113b18..8ca76e9044de 100644
--- a/drivers/net/wireless/ath/carl9170/main.c
+++ b/drivers/net/wireless/ath/carl9170/main.c
@@ -1545,7 +1545,7 @@ static int carl9170_rng_get(struct ar9170 *ar)
 
 	BUILD_BUG_ON(RB > CARL9170_MAX_CMD_PAYLOAD_LEN);
 
-	if (!IS_ACCEPTING_CMD(ar))
+	if (!IS_ACCEPTING_CMD(ar) || !ar->rng.initialized)
 		return -EAGAIN;
 
 	count = ARRAY_SIZE(ar->rng.cache);
@@ -1591,6 +1591,14 @@ static int carl9170_rng_read(struct hwrng *rng, u32 *data)
 	return sizeof(u16);
 }
 
+static void carl9170_unregister_hwrng(struct ar9170 *ar)
+{
+	if (ar->rng.initialized) {
+		hwrng_unregister(&ar->rng.rng);
+		ar->rng.initialized = false;
+	}
+}
+
 static int carl9170_register_hwrng(struct ar9170 *ar)
 {
 	int err;
@@ -1601,14 +1609,25 @@ static int carl9170_register_hwrng(struct ar9170 *ar)
 	ar->rng.rng.data_read = carl9170_rng_read;
 	ar->rng.rng.priv = (unsigned long)ar;
 
-	err = devm_hwrng_register(&ar->udev->dev, &ar->rng.rng);
+	if (WARN_ON(ar->rng.initialized))
+		return -EALREADY;
+
+	err = hwrng_register(&ar->rng.rng);
 	if (err) {
 		dev_err(&ar->udev->dev, "Failed to register the random "
 			"number generator (%d)\n", err);
 		return err;
 	}
 
-	return carl9170_rng_get(ar);
+	ar->rng.initialized = true;
+
+	err = carl9170_rng_get(ar);
+	if (err) {
+		carl9170_unregister_hwrng(ar);
+		return err;
+	}
+
+	return 0;
 }
 #endif /* CONFIG_CARL9170_HWRNG */
 
@@ -2053,6 +2072,10 @@ void carl9170_unregister(struct ar9170 *ar)
 	}
 #endif /* CONFIG_CARL9170_WPC */
 
+#ifdef CONFIG_CARL9170_HWRNG
+	carl9170_unregister_hwrng(ar);
+#endif /* CONFIG_CARL9170_HWRNG */
+
 	carl9170_cancel_worker(ar);
 	cancel_work_sync(&ar->restart_work);
 

-- 
2.56.0.rc1.315.gc6ed9934b7-goog