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>

4 files changed, 172 insertions, 0 deletions

diff --git a/tools/testing/selftests/tdx/.gitignore b/tools/testing/selftests/tdx/.gitignore
new file mode 100644
index 000000000..5db4d15cc
--- /dev/null
+++ b/tools/testing/selftests/tdx/.gitignore
@@ -0,0 +1 @@
+tdx_guest_test
diff --git a/tools/testing/selftests/tdx/Makefile b/tools/testing/selftests/tdx/Makefile
new file mode 100644
index 000000000..306e9c4d5
--- /dev/null
+++ b/tools/testing/selftests/tdx/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+
+CFLAGS += -O3 -Wl,-no-as-needed -Wall $(KHDR_INCLUDES) -static
+
+TEST_GEN_PROGS := tdx_guest_test
+
+include ../lib.mk
diff --git a/tools/testing/selftests/tdx/config b/tools/testing/selftests/tdx/config
new file mode 100644
index 000000000..aa1edc829
--- /dev/null
+++ b/tools/testing/selftests/tdx/config
@@ -0,0 +1 @@
+CONFIG_TDX_GUEST_DRIVER=y
diff --git a/tools/testing/selftests/tdx/tdx_guest_test.c b/tools/testing/selftests/tdx/tdx_guest_test.c
new file mode 100644
index 000000000..dfaefa685
--- /dev/null
+++ b/tools/testing/selftests/tdx/tdx_guest_test.c
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test TDX guest features
+ *
+ * Copyright (C) 2022 Intel Corporation.
+ *
+ * Author: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
+ */
+
+#include <sys/ioctl.h>
+
+#include <errno.h>
+#include <fcntl.h>
+
+#include <linux/tdx-guest.h>
+#include "kselftest_harness.h"
+
+#define TDX_GUEST_DEVNAME "/dev/tdx_guest"
+#define HEX_DUMP_SIZE 8
+#define DEBUG 0
+
+/**
+ * struct tdreport_type - Type header of TDREPORT_STRUCT.
+ * @type: Type of the TDREPORT (0 - SGX, 81 - TDX, rest are reserved)
+ * @sub_type: Subtype of the TDREPORT (Default value is 0).
+ * @version: TDREPORT version (Default value is 0).
+ * @reserved: Added for future extension.
+ *
+ * More details can be found in TDX v1.0 module specification, sec
+ * titled "REPORTTYPE".
+ */
+struct tdreport_type {
+	__u8 type;
+	__u8 sub_type;
+	__u8 version;
+	__u8 reserved;
+};
+
+/**
+ * struct reportmac - TDX guest report data, MAC and TEE hashes.
+ * @type: TDREPORT type header.
+ * @reserved1: Reserved for future extension.
+ * @cpu_svn: CPU security version.
+ * @tee_tcb_info_hash: SHA384 hash of TEE TCB INFO.
+ * @tee_td_info_hash: SHA384 hash of TDINFO_STRUCT.
+ * @reportdata: User defined unique data passed in TDG.MR.REPORT request.
+ * @reserved2: Reserved for future extension.
+ * @mac: CPU MAC ID.
+ *
+ * It is MAC-protected and contains hashes of the remainder of the
+ * report structure along with user provided report data. More details can
+ * be found in TDX v1.0 Module specification, sec titled "REPORTMACSTRUCT"
+ */
+struct reportmac {
+	struct tdreport_type type;
+	__u8 reserved1[12];
+	__u8 cpu_svn[16];
+	__u8 tee_tcb_info_hash[48];
+	__u8 tee_td_info_hash[48];
+	__u8 reportdata[64];
+	__u8 reserved2[32];
+	__u8 mac[32];
+};
+
+/**
+ * struct td_info - TDX guest measurements and configuration.
+ * @attr: TDX Guest attributes (like debug, spet_disable, etc).
+ * @xfam: Extended features allowed mask.
+ * @mrtd: Build time measurement register.
+ * @mrconfigid: Software-defined ID for non-owner-defined configuration
+ *              of the guest - e.g., run-time or OS configuration.
+ * @mrowner: Software-defined ID for the guest owner.
+ * @mrownerconfig: Software-defined ID for owner-defined configuration of
+ *                 the guest - e.g., specific to the workload.
+ * @rtmr: Run time measurement registers.
+ * @reserved: Added for future extension.
+ *
+ * It contains the measurements and initial configuration of the TDX guest
+ * that was locked at initialization and a set of measurement registers
+ * that are run-time extendable. More details can be found in TDX v1.0
+ * Module specification, sec titled "TDINFO_STRUCT".
+ */
+struct td_info {
+	__u8 attr[8];
+	__u64 xfam;
+	__u64 mrtd[6];
+	__u64 mrconfigid[6];
+	__u64 mrowner[6];
+	__u64 mrownerconfig[6];
+	__u64 rtmr[24];
+	__u64 reserved[14];
+};
+
+/*
+ * struct tdreport - Output of TDCALL[TDG.MR.REPORT].
+ * @reportmac: Mac protected header of size 256 bytes.
+ * @tee_tcb_info: Additional attestable elements in the TCB are not
+ *                reflected in the reportmac.
+ * @reserved: Added for future extension.
+ * @tdinfo: Measurements and configuration data of size 512 bytes.
+ *
+ * More details can be found in TDX v1.0 Module specification, sec
+ * titled "TDREPORT_STRUCT".
+ */
+struct tdreport {
+	struct reportmac reportmac;
+	__u8 tee_tcb_info[239];
+	__u8 reserved[17];
+	struct td_info tdinfo;
+};
+
+static void print_array_hex(const char *title, const char *prefix_str,
+			    const void *buf, int len)
+{
+	int i, j, line_len, rowsize = HEX_DUMP_SIZE;
+	const __u8 *ptr = buf;
+
+	printf("\t\t%s", title);
+
+	for (j = 0; j < len; j += rowsize) {
+		line_len = rowsize < (len - j) ? rowsize : (len - j);
+		printf("%s%.8x:", prefix_str, j);
+		for (i = 0; i < line_len; i++)
+			printf(" %.2x", ptr[j + i]);
+		printf("\n");
+	}
+
+	printf("\n");
+}
+
+TEST(verify_report)
+{
+	struct tdx_report_req req;
+	struct tdreport *tdreport;
+	int devfd, i;
+
+	devfd = open(TDX_GUEST_DEVNAME, O_RDWR | O_SYNC);
+	ASSERT_LT(0, devfd);
+
+	/* Generate sample report data */
+	for (i = 0; i < TDX_REPORTDATA_LEN; i++)
+		req.reportdata[i] = i;
+
+	/* Get TDREPORT */
+	ASSERT_EQ(0, ioctl(devfd, TDX_CMD_GET_REPORT0, &req));
+
+	if (DEBUG) {
+		print_array_hex("\n\t\tTDX report data\n", "",
+				req.reportdata, sizeof(req.reportdata));
+
+		print_array_hex("\n\t\tTDX tdreport data\n", "",
+				req.tdreport, sizeof(req.tdreport));
+	}
+
+	/* Make sure TDREPORT data includes the REPORTDATA passed */
+	tdreport = (struct tdreport *)req.tdreport;
+	ASSERT_EQ(0, memcmp(&tdreport->reportmac.reportdata[0],
+			    req.reportdata, sizeof(req.reportdata)));
+
+	ASSERT_EQ(0, close(devfd));
+}
+
+TEST_HARNESS_MAIN