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, 91 insertions, 0 deletions

diff --git a/include/sound/sdca.h b/include/sound/sdca.h
new file mode 100644
index 000000000..2bdf4e333
--- /dev/null
+++ b/include/sound/sdca.h
@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause) */
+/*
+ * The MIPI SDCA specification is available for public downloads at
+ * https://www.mipi.org/mipi-sdca-v1-0-download
+ *
+ * Copyright(c) 2024 Intel Corporation
+ */
+
+#ifndef __SDCA_H__
+#define __SDCA_H__
+
+#include <linux/types.h>
+#include <linux/kconfig.h>
+
+struct acpi_table_swft;
+struct fwnode_handle;
+struct sdw_slave;
+struct sdca_dev;
+
+#define SDCA_MAX_FUNCTION_COUNT 8
+
+/**
+ * struct sdca_function_desc - short descriptor for an SDCA Function
+ * @node: firmware node for the Function.
+ * @func_dev: pointer to SDCA function device.
+ * @name: Human-readable string.
+ * @type: Function topology type.
+ * @adr: ACPI address (used for SDCA register access).
+ * @duplicate: Internal flag to indicate if other functions of the same type
+ * exist.
+ */
+struct sdca_function_desc {
+	struct fwnode_handle *node;
+	struct sdca_dev *func_dev;
+	const char *name;
+	u32 type;
+	u8 adr;
+
+	bool duplicate;
+};
+
+/**
+ * struct sdca_device_data - structure containing all SDCA related information
+ * @interface_revision: Value read from _DSD property, mainly to check
+ * for changes between silicon versions.
+ * @num_functions: Total number of supported SDCA functions. Invalid/unsupported
+ * functions will be skipped.
+ * @function: Array of function descriptors.
+ * @swft: Pointer to the SWFT table, if available.
+ */
+struct sdca_device_data {
+	u32 interface_revision;
+	int num_functions;
+	struct sdca_function_desc function[SDCA_MAX_FUNCTION_COUNT];
+	struct acpi_table_swft *swft;
+};
+
+enum sdca_quirk {
+	SDCA_QUIRKS_RT712_VB,
+	SDCA_QUIRKS_SKIP_FUNC_TYPE_PATCHING,
+};
+
+#if IS_ENABLED(CONFIG_ACPI) && IS_ENABLED(CONFIG_SND_SOC_SDCA)
+
+void sdca_lookup_functions(struct sdw_slave *slave);
+void sdca_lookup_swft(struct sdw_slave *slave);
+void sdca_lookup_interface_revision(struct sdw_slave *slave);
+bool sdca_device_quirk_match(struct sdw_slave *slave, enum sdca_quirk quirk);
+int sdca_dev_register_functions(struct sdw_slave *slave);
+void sdca_dev_unregister_functions(struct sdw_slave *slave);
+
+#else
+
+static inline void sdca_lookup_functions(struct sdw_slave *slave) {}
+static inline void sdca_lookup_swft(struct sdw_slave *slave) {}
+static inline void sdca_lookup_interface_revision(struct sdw_slave *slave) {}
+static inline bool sdca_device_quirk_match(struct sdw_slave *slave, enum sdca_quirk quirk)
+{
+	return false;
+}
+
+static inline int sdca_dev_register_functions(struct sdw_slave *slave)
+{
+	return 0;
+}
+
+static inline void sdca_dev_unregister_functions(struct sdw_slave *slave) {}
+
+#endif
+
+#endif