From 1039bffd6ae9c75b42b7d148d6c1106134107b66 Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Tue, 28 Jul 2026 03:16:42 +0100 Subject: ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults 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 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) Reviewed-by: Linus Walleij Signed-off-by: Qi Xi Signed-off-by: Xie Yuanbin Signed-off-by: Russell King --- tools/perf/python/counting.py | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) create mode 100755 tools/perf/python/counting.py (limited to 'tools/perf/python/counting.py') diff --git a/tools/perf/python/counting.py b/tools/perf/python/counting.py new file mode 100755 index 000000000..02121d2bb --- /dev/null +++ b/tools/perf/python/counting.py @@ -0,0 +1,36 @@ +#!/usr/bin/env python3 +# SPDX-License-Identifier: GPL-2.0 +# -*- python -*- +# -*- coding: utf-8 -*- + +import argparse +import perf + +def main(event: str): + evlist = perf.parse_events(event) + + for evsel in evlist: + evsel.read_format = perf.FORMAT_TOTAL_TIME_ENABLED | perf.FORMAT_TOTAL_TIME_RUNNING + + evlist.open() + evlist.enable() + + count = 100000 + while count > 0: + count -= 1 + + evlist.disable() + + for evsel in evlist: + for cpu in evsel.cpus(): + for thread in evsel.threads(): + counts = evsel.read(cpu, thread) + print(f"For {evsel} val: {counts.val} enable: {counts.ena} run: {counts.run}") + + evlist.close() + +if __name__ == '__main__': + ap = argparse.ArgumentParser() + ap.add_argument('-e', '--event', help="Events to open", default="cpu-clock,task-clock") + args = ap.parse_args() + main(args.event) -- cgit v1.3.1