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, 129 insertions, 0 deletions

diff --git a/drivers/pinctrl/pinctrl-utils.c b/drivers/pinctrl/pinctrl-utils.c
new file mode 100644
index 000000000..b880e44b8
--- /dev/null
+++ b/drivers/pinctrl/pinctrl-utils.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Utils functions to implement the pincontrol driver.
+ *
+ * Copyright (c) 2013, NVIDIA Corporation.
+ *
+ * Author: Laxman Dewangan <ldewangan@nvidia.com>
+ */
+#include <linux/array_size.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+#include <linux/pinctrl/pinctrl.h>
+
+#include "core.h"
+#include "pinctrl-utils.h"
+
+int pinctrl_utils_reserve_map(struct pinctrl_dev *pctldev,
+		struct pinctrl_map **map, unsigned int *reserved_maps,
+		unsigned int *num_maps, unsigned int reserve)
+{
+	unsigned int old_num = *reserved_maps;
+	unsigned int new_num = *num_maps + reserve;
+	struct pinctrl_map *new_map;
+
+	if (old_num >= new_num)
+		return 0;
+
+	new_map = krealloc_array(*map, new_num, sizeof(*new_map), GFP_KERNEL);
+	if (!new_map) {
+		dev_err(pctldev->dev, "krealloc(map) failed\n");
+		return -ENOMEM;
+	}
+
+	memset(new_map + old_num, 0, (new_num - old_num) * sizeof(*new_map));
+
+	*map = new_map;
+	*reserved_maps = new_num;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pinctrl_utils_reserve_map);
+
+int pinctrl_utils_add_map_mux(struct pinctrl_dev *pctldev,
+		struct pinctrl_map **map, unsigned int *reserved_maps,
+		unsigned int *num_maps, const char *group,
+		const char *function)
+{
+	if (WARN_ON(*num_maps == *reserved_maps))
+		return -ENOSPC;
+
+	(*map)[*num_maps].type = PIN_MAP_TYPE_MUX_GROUP;
+	(*map)[*num_maps].data.mux.group = group;
+	(*map)[*num_maps].data.mux.function = function;
+	(*num_maps)++;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pinctrl_utils_add_map_mux);
+
+int pinctrl_utils_add_map_configs(struct pinctrl_dev *pctldev,
+		struct pinctrl_map **map, unsigned int *reserved_maps,
+		unsigned int *num_maps, const char *group,
+		unsigned long *configs, unsigned int num_configs,
+		enum pinctrl_map_type type)
+{
+	unsigned long *dup_configs;
+
+	if (WARN_ON(*num_maps == *reserved_maps))
+		return -ENOSPC;
+
+	dup_configs = kmemdup_array(configs, num_configs,
+				sizeof(*dup_configs), GFP_KERNEL);
+	if (!dup_configs)
+		return -ENOMEM;
+
+	(*map)[*num_maps].type = type;
+	(*map)[*num_maps].data.configs.group_or_pin = group;
+	(*map)[*num_maps].data.configs.configs = dup_configs;
+	(*map)[*num_maps].data.configs.num_configs = num_configs;
+	(*num_maps)++;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pinctrl_utils_add_map_configs);
+
+int pinctrl_utils_add_config(struct pinctrl_dev *pctldev,
+		unsigned long **configs, unsigned int *num_configs,
+		unsigned long config)
+{
+	unsigned int old_num = *num_configs;
+	unsigned int new_num = old_num + 1;
+	unsigned long *new_configs;
+
+	new_configs = krealloc(*configs, sizeof(*new_configs) * new_num,
+			       GFP_KERNEL);
+	if (!new_configs) {
+		dev_err(pctldev->dev, "krealloc(configs) failed\n");
+		return -ENOMEM;
+	}
+
+	new_configs[old_num] = config;
+
+	*configs = new_configs;
+	*num_configs = new_num;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pinctrl_utils_add_config);
+
+void pinctrl_utils_free_map(struct pinctrl_dev *pctldev,
+	      struct pinctrl_map *map, unsigned int num_maps)
+{
+	int i;
+
+	for (i = 0; i < num_maps; i++) {
+		switch (map[i].type) {
+		case PIN_MAP_TYPE_CONFIGS_GROUP:
+		case PIN_MAP_TYPE_CONFIGS_PIN:
+			kfree(map[i].data.configs.configs);
+			break;
+		default:
+			break;
+		}
+	}
+	kfree(map);
+}
+EXPORT_SYMBOL_GPL(pinctrl_utils_free_map);