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>

12 files changed, 12 insertions, 0 deletions

diff --git a/scripts/dtc/include-prefixes/arc b/scripts/dtc/include-prefixes/arc
new file mode 120000
index 000000000..5d21b5a69
--- /dev/null
+++ b/scripts/dtc/include-prefixes/arc
@@ -0,0 +1 @@
+../../../arch/arc/boot/dts
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/arm b/scripts/dtc/include-prefixes/arm
new file mode 120000
index 000000000..eb14d4515
--- /dev/null
+++ b/scripts/dtc/include-prefixes/arm
@@ -0,0 +1 @@
+../../../arch/arm/boot/dts
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/arm64 b/scripts/dtc/include-prefixes/arm64
new file mode 120000
index 000000000..275c42c21
--- /dev/null
+++ b/scripts/dtc/include-prefixes/arm64
@@ -0,0 +1 @@
+../../../arch/arm64/boot/dts
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/dt-bindings b/scripts/dtc/include-prefixes/dt-bindings
new file mode 120000
index 000000000..04fdbb3af
--- /dev/null
+++ b/scripts/dtc/include-prefixes/dt-bindings
@@ -0,0 +1 @@
+../../../include/dt-bindings
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/microblaze b/scripts/dtc/include-prefixes/microblaze
new file mode 120000
index 000000000..d9830330a
--- /dev/null
+++ b/scripts/dtc/include-prefixes/microblaze
@@ -0,0 +1 @@
+../../../arch/microblaze/boot/dts
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/mips b/scripts/dtc/include-prefixes/mips
new file mode 120000
index 000000000..ae8d4948d
--- /dev/null
+++ b/scripts/dtc/include-prefixes/mips
@@ -0,0 +1 @@
+../../../arch/mips/boot/dts
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/nios2 b/scripts/dtc/include-prefixes/nios2
new file mode 120000
index 000000000..51772336d
--- /dev/null
+++ b/scripts/dtc/include-prefixes/nios2
@@ -0,0 +1 @@
+../../../arch/nios2/boot/dts
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/openrisc b/scripts/dtc/include-prefixes/openrisc
new file mode 120000
index 000000000..71c3bc75c
--- /dev/null
+++ b/scripts/dtc/include-prefixes/openrisc
@@ -0,0 +1 @@
+../../../arch/openrisc/boot/dts
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/powerpc b/scripts/dtc/include-prefixes/powerpc
new file mode 120000
index 000000000..7cd6ec16e
--- /dev/null
+++ b/scripts/dtc/include-prefixes/powerpc
@@ -0,0 +1 @@
+../../../arch/powerpc/boot/dts
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/riscv b/scripts/dtc/include-prefixes/riscv
new file mode 120000
index 000000000..202509418
--- /dev/null
+++ b/scripts/dtc/include-prefixes/riscv
@@ -0,0 +1 @@
+../../../arch/riscv/boot/dts
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/sh b/scripts/dtc/include-prefixes/sh
new file mode 120000
index 000000000..67d37808c
--- /dev/null
+++ b/scripts/dtc/include-prefixes/sh
@@ -0,0 +1 @@
+../../../arch/sh/boot/dts
\ No newline at end of file
diff --git a/scripts/dtc/include-prefixes/xtensa b/scripts/dtc/include-prefixes/xtensa
new file mode 120000
index 000000000..d1eaf6ec7
--- /dev/null
+++ b/scripts/dtc/include-prefixes/xtensa
@@ -0,0 +1 @@
+../../../arch/xtensa/boot/dts
\ No newline at end of file