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, 89 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/tsc2005.c b/drivers/input/touchscreen/tsc2005.c
new file mode 100644
index 000000000..6fe8b41b3
--- /dev/null
+++ b/drivers/input/touchscreen/tsc2005.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * TSC2005 touchscreen driver
+ *
+ * Copyright (C) 2006-2010 Nokia Corporation
+ * Copyright (C) 2015 QWERTY Embedded Design
+ * Copyright (C) 2015 EMAC Inc.
+ *
+ * Based on original tsc2005.c by Lauri Leukkunen <lauri.leukkunen@nokia.com>
+ */
+
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/spi/spi.h>
+#include <linux/regmap.h>
+#include "tsc200x-core.h"
+
+static const struct input_id tsc2005_input_id = {
+	.bustype = BUS_SPI,
+	.product = 2005,
+};
+
+static int tsc2005_cmd(struct device *dev, u8 cmd)
+{
+	u8 tx = TSC200X_CMD | TSC200X_CMD_12BIT | cmd;
+	struct spi_transfer xfer = {
+		.tx_buf         = &tx,
+		.len            = 1,
+		.bits_per_word  = 8,
+	};
+	struct spi_message msg;
+	struct spi_device *spi = to_spi_device(dev);
+	int error;
+
+	spi_message_init(&msg);
+	spi_message_add_tail(&xfer, &msg);
+
+	error = spi_sync(spi, &msg);
+	if (error) {
+		dev_err(dev, "%s: failed, command: %x, spi error: %d\n",
+			__func__, cmd, error);
+		return error;
+	}
+
+	return 0;
+}
+
+static int tsc2005_probe(struct spi_device *spi)
+{
+	int error;
+
+	spi->mode = SPI_MODE_0;
+	spi->bits_per_word = 8;
+	if (!spi->max_speed_hz)
+		spi->max_speed_hz = TSC2005_SPI_MAX_SPEED_HZ;
+
+	error = spi_setup(spi);
+	if (error)
+		return error;
+
+	return tsc200x_probe(&spi->dev, spi->irq, &tsc2005_input_id,
+			     devm_regmap_init_spi(spi, &tsc200x_regmap_config),
+			     tsc2005_cmd);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id tsc2005_of_match[] = {
+	{ .compatible = "ti,tsc2005" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, tsc2005_of_match);
+#endif
+
+static struct spi_driver tsc2005_driver = {
+	.driver	= {
+		.name		= "tsc2005",
+		.dev_groups	= tsc200x_groups,
+		.of_match_table	= of_match_ptr(tsc2005_of_match),
+		.pm		= pm_sleep_ptr(&tsc200x_pm_ops),
+	},
+	.probe	= tsc2005_probe,
+};
+module_spi_driver(tsc2005_driver);
+
+MODULE_AUTHOR("Michael Welling <mwelling@ieee.org>");
+MODULE_DESCRIPTION("TSC2005 Touchscreen Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:tsc2005");