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, 42 insertions, 0 deletions

diff --git a/scripts/git.orderFile b/scripts/git.orderFile
new file mode 100644
index 000000000..5102ba733
--- /dev/null
+++ b/scripts/git.orderFile
@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# order file for git, to produce patches which are easier to review
+# by diffing the important stuff like header changes first.
+#
+# one-off usage:
+#   git diff -O scripts/git.orderFile ...
+#
+# add to git config:
+#   git config diff.orderFile scripts/git.orderFile
+#
+
+MAINTAINERS
+
+# Documentation
+Documentation/*
+*.rst
+
+# git-specific
+.gitignore
+scripts/git.orderFile
+
+# build system
+Kconfig*
+*/Kconfig*
+Kbuild*
+*/Kbuild*
+Makefile*
+*/Makefile*
+*.mak
+*.mk
+scripts/*
+
+# semantic patches
+*.cocci
+
+# headers
+*types.h
+*.h
+
+# code
+*.c