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 --- scripts/stackusage | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) create mode 100755 scripts/stackusage (limited to 'scripts/stackusage') diff --git a/scripts/stackusage b/scripts/stackusage new file mode 100755 index 000000000..56ef1ab67 --- /dev/null +++ b/scripts/stackusage @@ -0,0 +1,34 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 + +outfile="" +now=`date +%s` + +while [ $# -gt 0 ] +do + case "$1" in + -o) + outfile="$2" + shift 2;; + -h) + echo "usage: $0 [-o outfile] " + exit 0;; + *) break;; + esac +done + +if [ -z "$outfile" ] +then + outfile=`mktemp --tmpdir stackusage.$$.XXXX` +fi + +KCFLAGS="${KCFLAGS} -fstack-usage" make "$@" + +# Prepend directory name to file names, remove column information, +# make file:line/function/size/type properly tab-separated. +find . -name '*.su' -newermt "@${now}" -print | \ + xargs perl -MFile::Basename -pe \ + '$d = dirname($ARGV); s#([^:]+:[0-9]+):[0-9]+:#$d/$1\t#;' | \ + sort -k3,3nr > "${outfile}" + +echo "$0: output written to ${outfile}" -- cgit v1.3.1