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>

14 files changed, 164 insertions, 0 deletions

diff --git a/Documentation/dev-tools/lkmm/docs/access-marking.rst b/Documentation/dev-tools/lkmm/docs/access-marking.rst
new file mode 100644
index 000000000..80058a4da
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/access-marking.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Access Marking
+--------------
+
+Literal include of ``tools/memory-model/Documentation/access-marking.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/access-marking.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/cheatsheet.rst b/Documentation/dev-tools/lkmm/docs/cheatsheet.rst
new file mode 100644
index 000000000..37681f6a6
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/cheatsheet.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Cheatsheet
+----------
+
+Literal include of ``tools/memory-model/Documentation/cheatsheet.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/cheatsheet.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/control-dependencies.rst b/Documentation/dev-tools/lkmm/docs/control-dependencies.rst
new file mode 100644
index 000000000..5ae97e886
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/control-dependencies.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Control Dependencies
+--------------------
+
+Literal include of ``tools/memory-model/Documentation/control-dependencies.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/control-dependencies.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/explanation.rst b/Documentation/dev-tools/lkmm/docs/explanation.rst
new file mode 100644
index 000000000..0bcba9a5d
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/explanation.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Explanation
+-----------
+
+Literal include of ``tools/memory-model/Documentation/explanation.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/explanation.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/glossary.rst b/Documentation/dev-tools/lkmm/docs/glossary.rst
new file mode 100644
index 000000000..849aefdf3
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/glossary.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Glossary
+--------
+
+Literal include of ``tools/memory-model/Documentation/glossary.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/glossary.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/herd-representation.rst b/Documentation/dev-tools/lkmm/docs/herd-representation.rst
new file mode 100644
index 000000000..f7b41f286
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/herd-representation.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+herd-representation
+-------------------
+
+Literal include of ``tools/memory-model/Documentation/herd-representation.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/herd-representation.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/index.rst b/Documentation/dev-tools/lkmm/docs/index.rst
new file mode 100644
index 000000000..abbddcc00
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/index.rst
@@ -0,0 +1,21 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Documentation
+=============
+
+.. toctree::
+   :maxdepth: 1
+
+   readme
+   simple
+   ordering
+   litmus-tests
+   locking
+   recipes
+   control-dependencies
+   access-marking
+   cheatsheet
+   explanation
+   herd-representation
+   glossary
+   references
diff --git a/Documentation/dev-tools/lkmm/docs/litmus-tests.rst b/Documentation/dev-tools/lkmm/docs/litmus-tests.rst
new file mode 100644
index 000000000..3293f4540
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/litmus-tests.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Litmus Tests
+------------
+
+Literal include of ``tools/memory-model/Documentation/litmus-tests.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/litmus-tests.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/locking.rst b/Documentation/dev-tools/lkmm/docs/locking.rst
new file mode 100644
index 000000000..b5eae4c0a
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/locking.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Locking
+-------
+
+Literal include of ``tools/memory-model/Documentation/locking.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/locking.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/ordering.rst b/Documentation/dev-tools/lkmm/docs/ordering.rst
new file mode 100644
index 000000000..a2343c124
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/ordering.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Ordering
+--------
+
+Literal include of ``tools/memory-model/Documentation/ordering.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/ordering.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/readme.rst b/Documentation/dev-tools/lkmm/docs/readme.rst
new file mode 100644
index 000000000..51e7a64e4
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/readme.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+README (for LKMM Documentation)
+-------------------------------
+
+Literal include of ``tools/memory-model/Documentation/README``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/README
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/recipes.rst b/Documentation/dev-tools/lkmm/docs/recipes.rst
new file mode 100644
index 000000000..e55952640
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/recipes.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Recipes
+-------
+
+Literal include of ``tools/memory-model/Documentation/recipes.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/recipes.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/references.rst b/Documentation/dev-tools/lkmm/docs/references.rst
new file mode 100644
index 000000000..c6831b3c9
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/references.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+References
+----------
+
+Literal include of ``tools/memory-model/Documentation/references.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/references.txt
+   :literal:
diff --git a/Documentation/dev-tools/lkmm/docs/simple.rst b/Documentation/dev-tools/lkmm/docs/simple.rst
new file mode 100644
index 000000000..5c1094c95
--- /dev/null
+++ b/Documentation/dev-tools/lkmm/docs/simple.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Simple
+------
+
+Literal include of ``tools/memory-model/Documentation/simple.txt``.
+
+------------------------------------------------------------------
+
+.. kernel-include:: tools/memory-model/Documentation/simple.txt
+   :literal: