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, 18 insertions, 0 deletions

diff --git a/drivers/thunderbolt/Makefile b/drivers/thunderbolt/Makefile
new file mode 100644
index 000000000..beb054c31
--- /dev/null
+++ b/drivers/thunderbolt/Makefile
@@ -0,0 +1,18 @@
+# SPDX-License-Identifier: GPL-2.0-only
+ccflags-y := -I$(src)
+obj-${CONFIG_USB4} := thunderbolt.o
+thunderbolt-objs := nhi.o ctl.o tb.o switch.o cap.o pci.o path.o tunnel.o eeprom.o
+thunderbolt-objs += domain.o dma_port.o icm.o property.o xdomain.o lc.o tmu.o usb4.o
+thunderbolt-objs += usb4_port.o nvm.o retimer.o quirks.o clx.o
+
+thunderbolt-${CONFIG_ACPI} += acpi.o
+thunderbolt-$(CONFIG_DEBUG_FS) += debugfs.o
+thunderbolt-$(CONFIG_USB4_CONFIGFS) += configfs.o
+thunderbolt-${CONFIG_USB4_KUNIT_TEST} += test.o
+CFLAGS_test.o += $(DISABLE_STRUCTLEAK_PLUGIN)
+
+thunderbolt_dma_test-${CONFIG_USB4_DMA_TEST} += dma_test.o
+obj-$(CONFIG_USB4_DMA_TEST) += thunderbolt_dma_test.o
+
+thunderbolt_stream-${CONFIG_USB4_STREAM} += stream.o
+obj-$(CONFIG_USB4_STREAM) += thunderbolt_stream.o