[PATCH v2] crypto: atmel-sha204a - Fix potential UAF and memory leak in remove path

[Thorsten Blum]

Unregister the hwrng to prevent new ->read() calls and flush the Atmel
I2C workqueue before teardown to prevent a potential UAF if a queued
callback runs while the device is being removed.

Drop the early return to ensure sysfs entries are removed and
->hwrng.priv is freed, preventing a memory leak.

Fixes: da001fb651b0 ("crypto: atmel-i2c - add support for SHA204A random number generator")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Thorsten Blum <thorsten.blum@xxxxxxxxx>
---
Changes in v2:
- Unregister hwrng to avoid new ->read() calls and then flush the queue
- Drop the ->tfm_count check and error logging after flushing (Herbert)
- Link to v1: https://lore.kernel.org/lkml/20260221190424.85984-2-thorsten.blum@xxxxxxxxx/
---
 drivers/crypto/atmel-sha204a.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/atmel-sha204a.c b/drivers/crypto/atmel-sha204a.c
index 98d1023007e3..aeadbc9a2759 100644
--- a/drivers/crypto/atmel-sha204a.c
+++ b/drivers/crypto/atmel-sha204a.c
@@ -191,10 +191,8 @@ static void atmel_sha204a_remove(struct i2c_client *client)
 {
 	struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
 
-	if (atomic_read(&i2c_priv->tfm_count)) {
-		dev_emerg(&client->dev, "Device is busy, will remove it anyhow\n");
-		return;
-	}
+	devm_hwrng_unregister(&client->dev, &i2c_priv->hwrng);
+	atmel_i2c_flush_queue();
 
 	sysfs_remove_group(&client->dev.kobj, &atmel_sha204a_groups);