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, 57 insertions, 0 deletions

diff --git a/include/soc/tegra/common.h b/include/soc/tegra/common.h
new file mode 100644
index 000000000..8ec1ac07f
--- /dev/null
+++ b/include/soc/tegra/common.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2014 NVIDIA Corporation
+ */
+
+#ifndef __SOC_TEGRA_COMMON_H__
+#define __SOC_TEGRA_COMMON_H__
+
+#include <linux/errno.h>
+#include <linux/types.h>
+
+struct device;
+
+/**
+ * Tegra SoC core device OPP table configuration
+ *
+ * @init_state: pre-initialize OPP state of a device
+ */
+struct tegra_core_opp_params {
+	bool init_state;
+};
+
+#ifdef CONFIG_ARCH_TEGRA
+bool soc_is_tegra(void);
+
+int devm_tegra_core_dev_init_opp_table(struct device *dev,
+				       struct tegra_core_opp_params *params);
+#else
+static inline bool soc_is_tegra(void)
+{
+	return false;
+}
+
+static inline int
+devm_tegra_core_dev_init_opp_table(struct device *dev,
+				   struct tegra_core_opp_params *params)
+{
+	return -ENODEV;
+}
+#endif
+
+static inline int
+devm_tegra_core_dev_init_opp_table_common(struct device *dev)
+{
+	struct tegra_core_opp_params opp_params = {};
+	int err;
+
+	opp_params.init_state = true;
+
+	err = devm_tegra_core_dev_init_opp_table(dev, &opp_params);
+	if (err != -ENODEV)
+		return err;
+
+	return 0;
+}
+
+#endif /* __SOC_TEGRA_COMMON_H__ */