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, 152 insertions, 0 deletions

diff --git a/include/uapi/misc/amd-apml.h b/include/uapi/misc/amd-apml.h
new file mode 100644
index 000000000..745b3338f
--- /dev/null
+++ b/include/uapi/misc/amd-apml.h
@@ -0,0 +1,152 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Copyright (C) 2021-2024 Advanced Micro Devices, Inc.
+ */
+#ifndef _AMD_APML_H_
+#define _AMD_APML_H_
+
+#include <linux/types.h>
+
+/* Mailbox data size for data_in and data_out */
+#define AMD_SBI_MB_DATA_SIZE		4
+
+struct apml_mbox_msg {
+	/*
+	 * Mailbox Message ID
+	 */
+	__u32 cmd;
+	/*
+	 * [0]...[3] mailbox 32bit input/output data
+	 */
+	__u32 mb_in_out;
+	/*
+	 * Error code is returned in case of soft mailbox error
+	 */
+	__u32 fw_ret_code;
+};
+
+struct apml_cpuid_msg {
+	/*
+	 * CPUID input
+	 * [0]...[3] cpuid func,
+	 * [4][5] cpuid: thread
+	 * [6] cpuid: ext function & read eax/ebx or ecx/edx
+	 *	[7:0] -> bits [7:4] -> ext function &
+	 *	bit [0] read eax/ebx or ecx/edx
+	 * CPUID output
+	 */
+	__u64 cpu_in_out;
+	/*
+	 * Status code for CPUID read
+	 */
+	__u32 fw_ret_code;
+	__u32 pad;
+};
+
+struct apml_mcamsr_msg {
+	/*
+	 * MCAMSR input
+	 * [0]...[3] mca msr func,
+	 * [4][5] thread
+	 * MCAMSR output
+	 */
+	__u64 mcamsr_in_out;
+	/*
+	 * Status code for MCA/MSR access
+	 */
+	__u32 fw_ret_code;
+	__u32 pad;
+};
+
+struct apml_reg_xfer_msg {
+	/*
+	 * RMI register address offset
+	 */
+	__u16 reg_addr;
+	/*
+	 * Register data for read/write
+	 */
+	__u8 data_in_out;
+	/*
+	 * Register read or write
+	 */
+	__u8 rflag;
+};
+
+/*
+ * AMD sideband interface base IOCTL
+ */
+#define SB_BASE_IOCTL_NR	0xF9
+
+/**
+ * DOC: SBRMI_IOCTL_MBOX_CMD
+ *
+ * @Parameters
+ *
+ * @struct apml_mbox_msg
+ *	Pointer to the &struct apml_mbox_msg that will contain the protocol
+ *	information
+ *
+ * @Description
+ * IOCTL command for APML messages using generic _IOWR
+ * The IOCTL provides userspace access to AMD sideband mailbox protocol
+ * - Mailbox message read/write(0x0~0xFF)
+ * - returning "-EFAULT" if none of the above
+ * "-EPROTOTYPE" error is returned to provide additional error details
+ */
+#define SBRMI_IOCTL_MBOX_CMD		_IOWR(SB_BASE_IOCTL_NR, 0, struct apml_mbox_msg)
+
+/**
+ * DOC: SBRMI_IOCTL_CPUID_CMD
+ *
+ * @Parameters
+ *
+ * @struct apml_cpuid_msg
+ *	Pointer to the &struct apml_cpuid_msg that will contain the protocol
+ *	information
+ *
+ * @Description
+ * IOCTL command for APML messages using generic _IOWR
+ * The IOCTL provides userspace access to AMD sideband cpuid protocol
+ * - CPUID protocol to get CPU details for Function/Ext Function
+ * at thread level
+ * - returning "-EFAULT" if none of the above
+ * "-EPROTOTYPE" error is returned to provide additional error details
+ */
+#define SBRMI_IOCTL_CPUID_CMD		_IOWR(SB_BASE_IOCTL_NR, 1, struct apml_cpuid_msg)
+
+/**
+ * DOC: SBRMI_IOCTL_MCAMSR_CMD
+ *
+ * @Parameters
+ *
+ * @struct apml_mcamsr_msg
+ *	Pointer to the &struct apml_mcamsr_msg that will contain the protocol
+ *	information
+ *
+ * @Description
+ * IOCTL command for APML messages using generic _IOWR
+ * The IOCTL provides userspace access to AMD sideband MCAMSR protocol
+ * - MCAMSR protocol to get MCA bank details for Function at thread level
+ * - returning "-EFAULT" if none of the above
+ * "-EPROTOTYPE" error is returned to provide additional error details
+ */
+#define SBRMI_IOCTL_MCAMSR_CMD		_IOWR(SB_BASE_IOCTL_NR, 2, struct apml_mcamsr_msg)
+
+/**
+ * DOC: SBRMI_IOCTL_REG_XFER_CMD
+ *
+ * @Parameters
+ *
+ * @struct apml_reg_xfer_msg
+ *	Pointer to the &struct apml_reg_xfer_msg that will contain the protocol
+ *	information
+ *
+ * @Description
+ * IOCTL command for APML messages using generic _IOWR
+ * The IOCTL provides userspace access to AMD sideband register xfer protocol
+ * - Register xfer protocol to get/set hardware register for given offset
+ */
+#define SBRMI_IOCTL_REG_XFER_CMD	_IOWR(SB_BASE_IOCTL_NR, 3, struct apml_reg_xfer_msg)
+
+#endif /*_AMD_APML_H_*/