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, 88 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/fuse/nvidia,tegra20-fuse.yaml b/Documentation/devicetree/bindings/fuse/nvidia,tegra20-fuse.yaml
new file mode 100644
index 000000000..02f0b0462
--- /dev/null
+++ b/Documentation/devicetree/bindings/fuse/nvidia,tegra20-fuse.yaml
@@ -0,0 +1,88 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/fuse/nvidia,tegra20-fuse.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NVIDIA Tegra FUSE block
+
+maintainers:
+  - Thierry Reding <thierry.reding@gmail.com>
+  - Jon Hunter <jonathanh@nvidia.com>
+
+properties:
+  compatible:
+    oneOf:
+      - enum:
+          - nvidia,tegra20-efuse
+          - nvidia,tegra30-efuse
+          - nvidia,tegra114-efuse
+          - nvidia,tegra124-efuse
+          - nvidia,tegra210-efuse
+          - nvidia,tegra186-efuse
+          - nvidia,tegra194-efuse
+          - nvidia,tegra234-efuse
+
+      - items:
+          - const: nvidia,tegra132-efuse
+          - const: nvidia,tegra124-efuse
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    items:
+      - const: fuse
+
+  resets:
+    maxItems: 1
+
+  reset-names:
+    items:
+      - const: fuse
+
+  operating-points-v2: true
+
+  power-domains:
+    items:
+      - description: phandle to the core power domain
+
+additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+
+if:
+  properties:
+    compatible:
+      contains:
+        enum:
+          - nvidia,tegra20-efuse
+          - nvidia,tegra30-efuse
+          - nvidia,tegra114-efuse
+          - nvidia,tegra124-efuse
+          - nvidia,tegra132-efuse
+          - nvidia,tegra210-efuse
+then:
+  required:
+    - resets
+    - reset-names
+
+examples:
+  - |
+    #include <dt-bindings/clock/tegra20-car.h>
+
+    fuse@7000f800 {
+        compatible = "nvidia,tegra20-efuse";
+        reg = <0x7000f800 0x400>;
+        clocks = <&tegra_car TEGRA20_CLK_FUSE>;
+        clock-names = "fuse";
+        resets = <&tegra_car 39>;
+        reset-names = "fuse";
+    };