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/extract-vmlinux | 65 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100755 scripts/extract-vmlinux (limited to 'scripts/extract-vmlinux') diff --git a/scripts/extract-vmlinux b/scripts/extract-vmlinux new file mode 100755 index 000000000..266df9bc7 --- /dev/null +++ b/scripts/extract-vmlinux @@ -0,0 +1,65 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0-only +# ---------------------------------------------------------------------- +# extract-vmlinux - Extract uncompressed vmlinux from a kernel image +# +# Inspired from extract-ikconfig +# (c) 2009,2010 Dick Streefland +# +# (c) 2011 Corentin Chary +# +# ---------------------------------------------------------------------- + +me=${0##*/} + +check_vmlinux() +{ + if file "$1" | grep -q 'Linux kernel.*boot executable' || + readelf -h "$1" > /dev/null 2>&1 + then + cat "$1" + echo "$me: Extracted vmlinux using '$2' from offset $3" >&2 + exit 0 + fi +} + +try_decompress() +{ + # The obscure use of the "tr" filter is to work around older versions of + # "grep" that report the byte offset of the line instead of the pattern. + + # Try to find the header ($1) and decompress from here + for pos in `tr "$1\n$2" "\n$2=" < "$img" | grep -abo "^$2"` + do + pos=${pos%%:*} + tail -c+$pos "$img" | $3 > $tmp 2> /dev/null + check_vmlinux $tmp "$3" $pos + done +} + +# Check invocation: +img=$1 +if [ $# -ne 1 -o ! -s "$img" ] +then + echo "Usage: $me " >&2 + exit 2 +fi + +# Prepare temp files: +tmp=$(mktemp /tmp/vmlinux-XXX) +trap "rm -f $tmp" 0 + +# That didn't work, so retry after decompression. +try_decompress '\037\213\010' xy gunzip +try_decompress '\3757zXZ\000' abcde unxz +try_decompress 'BZh' xy bunzip2 +try_decompress '\135\0\0\0' xxx unlzma +try_decompress '\211\114\132' xy 'lzop -d' +try_decompress '\002!L\030' xxx 'lz4 -d' +try_decompress '(\265/\375' xxx unzstd + +# Finally check for uncompressed images or objects: +check_vmlinux "$img" cat 0 + +# Bail out: +echo "$me: Cannot find vmlinux." >&2 -- cgit v1.3.1