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/livepatch/fix-patch-lines | 79 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+) create mode 100755 scripts/livepatch/fix-patch-lines (limited to 'scripts/livepatch/fix-patch-lines') diff --git a/scripts/livepatch/fix-patch-lines b/scripts/livepatch/fix-patch-lines new file mode 100755 index 000000000..fa7d4f659 --- /dev/null +++ b/scripts/livepatch/fix-patch-lines @@ -0,0 +1,79 @@ +#!/usr/bin/awk -f +# SPDX-License-Identifier: GPL-2.0 +# +# Use #line directives to preserve original __LINE__ numbers across patches to +# avoid unwanted compilation changes. + +BEGIN { + in_hunk = 0 + skip = 0 +} + +/^--- / { + skip = $2 !~ /\.(c|h)$/ + print + next +} + +/^@@/ { + if (skip) { + print + next + } + + in_hunk = 1 + + # @@ -1,3 +1,4 @@: + # 1: line number in old file + # 3: how many lines the hunk covers in old file + # 1: line number in new file + # 4: how many lines the hunk covers in new file + + match($0, /^@@ -([0-9]+)(,([0-9]+))? \+([0-9]+)(,([0-9]+))? @@/, m) + + # Set 'cur' to the old file's line number at the start of the hunk. It + # gets incremented for every context line and every line removal, so + # that it always represents the old file's current line number. + cur = m[1] + + # last = last line number of current hunk + last = cur + (m[3] ? m[3] : 1) - 1 + + need_line_directive = 0 + + print + next +} + +{ + if (skip || !in_hunk || $0 ~ /^\\ No newline at end of file/) { + print + next + } + + # change line + if ($0 ~ /^[+-]/) { + # inject #line after this group of changes + need_line_directive = 1 + + if ($0 ~ /^-/) + cur++ + + print + next + } + + # If this is the first context line after a group of changes, inject + # the #line directive to force the compiler to correct the line + # numbering to match the original file. + if (need_line_directive) { + print "+#line " cur + need_line_directive = 0 + } + + if (cur == last) + in_hunk = 0 + + cur++ + print +} -- cgit v1.3.1