[PATCH v5 3/6] ata: sata_fsl: Fix use-after-free of host_priv on probe() failure

[Niklas Cassel <cassel@kernel.org>]

sata_fsl_host_stop() releases hcr_base and host_priv:

	static void sata_fsl_host_stop(struct ata_host *host)
	{
		struct sata_fsl_host_priv *host_priv = host->private_data;

		iounmap(host_priv->hcr_base);
		kfree(host_priv);
	}

->host_stop() is called by the driver core through the ata_host_stop()
devres action which ata_host_start() registers, so it is called both when
the device is unbound and when probe() fails after the host has been
started.

The error_exit_with_cleanup label of sata_fsl_probe() releases hcr_base
and host_priv as well, and it is reachable from the two
device_create_file() calls which are done after the host has been
activated. In that case sata_fsl_host_stop() runs on an already freed
host_priv, resulting in a use-after-free and a double iounmap()/kfree().

Add a separate error label for the failures happening after the host has
been activated, which only detaches the host and leaves hcr_base and
host_priv to sata_fsl_host_stop().

Note that ata_host_detach() is dropped from error_exit_with_cleanup, as
that label is now only reachable while host is still NULL.

Fixes: 6c8ad7e8cf29 ("sata_fsl: fix UAF in sata_fsl_port_stop when rmmod sata_fsl")
Cc: stable@vger.kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/ata/sata_fsl.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/ata/sata_fsl.c b/drivers/ata/sata_fsl.c
index 70b210afd291..4037dd758f87 100644
--- a/drivers/ata/sata_fsl.c
+++ b/drivers/ata/sata_fsl.c
@@ -1500,7 +1500,7 @@ static int sata_fsl_probe(struct platform_device *ofdev)
 	host_priv->intr_coalescing.attr.mode = S_IRUGO | S_IWUSR;
 	retval = device_create_file(host->dev, &host_priv->intr_coalescing);
 	if (retval)
-		goto error_exit_with_cleanup;
+		goto error_exit_detach;
 
 	host_priv->rx_watermark.show = fsl_sata_rx_watermark_show;
 	host_priv->rx_watermark.store = fsl_sata_rx_watermark_store;
@@ -1510,16 +1510,24 @@ static int sata_fsl_probe(struct platform_device *ofdev)
 	retval = device_create_file(host->dev, &host_priv->rx_watermark);
 	if (retval) {
 		device_remove_file(&ofdev->dev, &host_priv->intr_coalescing);
-		goto error_exit_with_cleanup;
+		goto error_exit_detach;
 	}
 
 	return 0;
 
-error_exit_with_cleanup:
+	/*
+	 * Once the host has been activated, hcr_base and host_priv are
+	 * released by sata_fsl_host_stop(), which is called by the driver core
+	 * through the ata_host_stop() devres action registered by
+	 * ata_host_start(). Releasing them here as well would result in a
+	 * double iounmap() and a use-after-free.
+	 */
+error_exit_detach:
+	ata_host_detach(host);
 
-	if (host)
-		ata_host_detach(host);
+	return retval;
 
+error_exit_with_cleanup:
 	if (hcr_base)
 		iounmap(hcr_base);
 	kfree(host_priv);
-- 
2.55.0