ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faultsgrafted

When CONFIG_DEBUG_USER=y, and cmdline "user_debug=31" is set,
a user fault may trigger show_pte() without any lock.
If another thread in the same process concurrently calls munmap(),
the page table pages may be freed while show_pte() is still traversing
them, causing a use-after-free in show_pte().

If CONFIG_ARM_LPAE=y, this may cause a kernel panic if the pages table
of PMD are freed when show_pte() is running.

Acquire mmap_write_lock() around show_pte() for user faults to fix the
contention.

For user faults, additionally restrict that show_pte() is called only
when the addr is a user-space address (addr < TASK_SIZE). This is because
the lock of tsk->mm only protects the virtual memory of user address space,
furthermore, dumping the page tables of a kernel-space address for user
faults is unnecessary and may have security implications.

Keep everything unchanged for kernel faults, because the kernel is
already in the "oops" state, acquiring a lock may risk a deadlock.

Co-developed-by: Qi Xi <xiqi2@huawei.com>

Fixes: 6d021b724481 ("ARM: dump pgd, pmd and pte states on unhandled data abort faults")
Link: https://lore.kernel.org/20260716014022.2823-1-xieyuanbin1@huawei.com
Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Qi Xi <xiqi2@huawei.com>
Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 122 insertions, 0 deletions

diff --git a/drivers/reset/reset-raspberrypi.c b/drivers/reset/reset-raspberrypi.c
new file mode 100644
index 000000000..fa23db554
--- /dev/null
+++ b/drivers/reset/reset-raspberrypi.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Raspberry Pi 4 firmware reset driver
+ *
+ * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
+ */
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+#include <dt-bindings/reset/raspberrypi,firmware-reset.h>
+
+struct rpi_reset {
+	struct reset_controller_dev rcdev;
+	struct rpi_firmware *fw;
+};
+
+static inline struct rpi_reset *to_rpi(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct rpi_reset, rcdev);
+}
+
+static int rpi_reset_reset(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct rpi_reset *priv = to_rpi(rcdev);
+	u32 dev_addr;
+	int ret;
+
+	switch (id) {
+	case RASPBERRYPI_FIRMWARE_RESET_ID_USB:
+		/*
+		 * The Raspberry Pi 4 gets its USB functionality from VL805, a
+		 * PCIe chip that implements xHCI. After a PCI reset, VL805's
+		 * firmware may either be loaded directly from an EEPROM or, if
+		 * not present, by the SoC's co-processor, VideoCore. rpi's
+		 * VideoCore OS contains both the non public firmware load
+		 * logic and the VL805 firmware blob. This triggers the
+		 * aforementioned process.
+		 *
+		 * The pci device address is expected is expected by the
+		 * firmware encoded like this:
+		 *
+		 *	PCI_BUS << 20 | PCI_SLOT << 15 | PCI_FUNC << 12
+		 *
+		 * But since rpi's PCIe is hardwired, we know the address in
+		 * advance.
+		 */
+		dev_addr = 0x100000;
+		ret = rpi_firmware_property(priv->fw, RPI_FIRMWARE_NOTIFY_XHCI_RESET,
+					    &dev_addr, sizeof(dev_addr));
+		if (ret)
+			return ret;
+
+		/* Wait for vl805 to startup */
+		usleep_range(200, 1000);
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct reset_control_ops rpi_reset_ops = {
+	.reset	= rpi_reset_reset,
+};
+
+static int rpi_reset_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct rpi_firmware *fw;
+	struct device_node *np;
+	struct rpi_reset *priv;
+
+	np = of_get_parent(dev->of_node);
+	if (!np) {
+		dev_err(dev, "Missing firmware node\n");
+		return -ENOENT;
+	}
+
+	fw = devm_rpi_firmware_get(&pdev->dev, np);
+	of_node_put(np);
+	if (!fw)
+		return -EPROBE_DEFER;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, priv);
+
+	priv->fw = fw;
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.nr_resets = RASPBERRYPI_FIRMWARE_RESET_NUM_IDS;
+	priv->rcdev.ops = &rpi_reset_ops;
+	priv->rcdev.of_node = dev->of_node;
+
+	return devm_reset_controller_register(dev, &priv->rcdev);
+}
+
+static const struct of_device_id rpi_reset_of_match[] = {
+	{ .compatible = "raspberrypi,firmware-reset" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, rpi_reset_of_match);
+
+static struct platform_driver rpi_reset_driver = {
+	.probe	= rpi_reset_probe,
+	.driver	= {
+		.name = "raspberrypi-reset",
+		.of_match_table = rpi_reset_of_match,
+	},
+};
+module_platform_driver(rpi_reset_driver);
+
+MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
+MODULE_DESCRIPTION("Raspberry Pi 4 firmware reset driver");
+MODULE_LICENSE("GPL");