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, 92 insertions, 0 deletions

diff --git a/tools/perf/util/debug.h b/tools/perf/util/debug.h
new file mode 100644
index 000000000..6b737e195
--- /dev/null
+++ b/tools/perf/util/debug.h
@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* For debugging general purposes */
+#ifndef __PERF_DEBUG_H
+#define __PERF_DEBUG_H
+
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <linux/compiler.h>
+
+extern int verbose;
+extern int debug_kmaps;
+extern int debug_peo_args;
+extern bool quiet, dump_trace;
+extern int debug_ordered_events;
+extern int debug_data_convert;
+extern int debug_type_profile;
+
+#ifndef pr_fmt
+#define pr_fmt(fmt) fmt
+#endif
+
+#define pr_err(fmt, ...) \
+	eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_warning(fmt, ...) \
+	eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_warning_once(fmt, ...) ({		\
+	static int __warned;			\
+	if (unlikely(!__warned)) {		\
+		pr_warning(fmt, ##__VA_ARGS__); \
+		__warned = 1;			\
+	}					\
+})
+#define pr_info(fmt, ...) \
+	eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debug(fmt, ...) \
+	eprintf(1, verbose, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debugN(n, fmt, ...) \
+	eprintf(n, verbose, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debug2(fmt, ...) pr_debugN(2, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debug3(fmt, ...) pr_debugN(3, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debug4(fmt, ...) pr_debugN(4, pr_fmt(fmt), ##__VA_ARGS__)
+
+/* Special macro to print perf_event_open arguments/return value. */
+#define pr_debug2_peo(fmt, ...) {				\
+	if (debug_peo_args)						\
+		pr_debugN(0, pr_fmt(fmt), ##__VA_ARGS__);	\
+	else							\
+		pr_debugN(2, pr_fmt(fmt), ##__VA_ARGS__);	\
+}
+
+#define pr_time_N(n, var, t, fmt, ...) \
+	eprintf_time(n, var, t, fmt, ##__VA_ARGS__)
+
+#define pr_oe_time(t, fmt, ...)  pr_time_N(1, debug_ordered_events, t, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_oe_time2(t, fmt, ...) pr_time_N(2, debug_ordered_events, t, pr_fmt(fmt), ##__VA_ARGS__)
+
+#define STRERR_BUFSIZE	128	/* For the buffer size of str_error_r */
+
+union perf_event;
+
+int dump_printf(const char *fmt, ...) __printf(1, 2);
+void trace_event(union perf_event *event);
+
+int ui__error(const char *format, ...) __printf(1, 2);
+int ui__warning(const char *format, ...) __printf(1, 2);
+#define ui__warning_once(format, ...) ({		\
+	static int __warned;				\
+	if (unlikely(!__warned)) {			\
+		ui__warning(format, ##__VA_ARGS__);	\
+		__warned = 1;				\
+	}						\
+})
+
+void pr_stat(const char *fmt, ...);
+
+int eprintf(int level, int var, const char *fmt, ...) __printf(3, 4);
+int eprintf_time(int level, int var, u64 t, const char *fmt, ...) __printf(4, 5);
+int veprintf(int level, int var, const char *fmt, va_list args);
+
+int perf_debug_option(const char *str);
+FILE *debug_file(void);
+void debug_set_file(FILE *file);
+void debug_set_display_time(bool set);
+void perf_debug_setup(void);
+int perf_quiet_option(void);
+
+void __dump_stack(FILE *file, void **stackdump, size_t stackdump_size);
+void dump_stack(void);
+void sighandler_dump_stack(int sig);
+
+#endif	/* __PERF_DEBUG_H */