linux-kernel - [PATCH 3/5] bus: hisi_lpc: Unregister logical PIO range to avoid potential use-after-free

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Date:   Thu, 20 Jun 2019 18:31:54 +0800
From:   John Garry <john.garry@...wei.com>
To:     <xuwei5@...wei.com>
CC:     <bhelgaas@...gle.com>, <linuxarm@...wei.com>, <arm@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <joe@...ches.com>, John Garry <john.garry@...wei.com>
Subject: [PATCH 3/5] bus: hisi_lpc: Unregister logical PIO range to avoid potential use-after-free

If, after registering a logical PIO range, the driver probe later fails,
the logical PIO range memory will be released automatically.

This causes an issue, in that the logical PIO range is not unregistered
and the released range memory may be later referenced.

Fix by unregistering the logical PIO range.

And since we now unregister the logical PIO range for probe failure, avoid
the special ordering of setting logical PIO range ops, which was a
previous (poor) attempt at a safeguard against this.

Fixes: adf38bb0b595 ("HISI LPC: Support the LPC host on Hip06/Hip07 with DT bindings")
Signed-off-by: John Garry <john.garry@...wei.com>
---
 drivers/bus/hisi_lpc.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/bus/hisi_lpc.c b/drivers/bus/hisi_lpc.c
index 19d7b6ff2f17..6d301aafcad2 100644
--- a/drivers/bus/hisi_lpc.c
+++ b/drivers/bus/hisi_lpc.c
@@ -606,24 +606,25 @@ static int hisi_lpc_probe(struct platform_device *pdev)
 	range->fwnode = dev->fwnode;
 	range->flags = LOGIC_PIO_INDIRECT;
 	range->size = PIO_INDIRECT_SIZE;
+	range->hostdata = lpcdev;
+	range->ops = &hisi_lpc_ops;
+	lpcdev->io_host = range;
 
 	ret = logic_pio_register_range(range);
 	if (ret) {
 		dev_err(dev, "register IO range failed (%d)!\n", ret);
 		return ret;
 	}
-	lpcdev->io_host = range;
 
 	/* register the LPC host PIO resources */
 	if (acpi_device)
 		ret = hisi_lpc_acpi_probe(dev);
 	else
 		ret = of_platform_populate(dev->of_node, NULL, NULL, dev);
-	if (ret)
+	if (ret) {
+		logic_pio_unregister_range(range);
 		return ret;
-
-	lpcdev->io_host->hostdata = lpcdev;
-	lpcdev->io_host->ops = &hisi_lpc_ops;
+	}
 
 	io_end = lpcdev->io_host->io_start + lpcdev->io_host->size;
 	dev_info(dev, "registered range [%pa - %pa]\n",
-- 
2.17.1