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, 69 insertions, 0 deletions

diff --git a/scripts/Makefile b/scripts/Makefile
new file mode 100644
index 000000000..3434a82a1
--- /dev/null
+++ b/scripts/Makefile
@@ -0,0 +1,69 @@
+# SPDX-License-Identifier: GPL-2.0
+###
+# scripts contains sources for various helper programs used throughout
+# the kernel for the build process.
+
+hostprogs-always-$(CONFIG_KALLSYMS)			+= kallsyms
+hostprogs-always-$(BUILD_C_RECORDMCOUNT)		+= recordmcount
+hostprogs-always-$(CONFIG_BUILDTIME_TABLE_SORT)		+= sorttable
+hostprogs-always-$(CONFIG_ASN1)				+= asn1_compiler
+hostprogs-always-$(CONFIG_MODULE_SIG_FORMAT)		+= sign-file
+hostprogs-always-$(CONFIG_SYSTEM_EXTRA_CERTIFICATE)	+= insert-sys-cert
+hostprogs-always-$(CONFIG_RUST_KERNEL_DOCTESTS)		+= rustdoc_test_builder
+hostprogs-always-$(CONFIG_RUST_KERNEL_DOCTESTS)		+= rustdoc_test_gen
+hostprogs-always-$(CONFIG_TRACEPOINTS)			+= tracepoint-update
+
+sorttable-objs := sorttable.o elf-parse.o
+tracepoint-update-objs := tracepoint-update.o elf-parse.o
+
+ifneq ($(or $(CONFIG_X86_64),$(CONFIG_X86_32)),)
+always-$(CONFIG_RUST)					+= target.json
+filechk_rust_target = $< < include/config/auto.conf
+
+$(obj)/target.json: scripts/generate_rust_target include/config/auto.conf FORCE
+	$(call filechk,rust_target)
+endif
+
+hostprogs += generate_rust_target
+generate_rust_target-rust := y
+rustdoc_test_builder-rust := y
+rustdoc_test_gen-rust := y
+
+HOSTCFLAGS_tracepoint-update.o = -I$(srctree)/tools/include
+HOSTCFLAGS_elf-parse.o = -I$(srctree)/tools/include
+HOSTCFLAGS_sorttable.o = -I$(srctree)/tools/include
+HOSTLDLIBS_sorttable = -lpthread
+HOSTCFLAGS_asn1_compiler.o = -I$(srctree)/include
+HOSTCFLAGS_sign-file.o = $(shell $(HOSTPKG_CONFIG) --cflags libcrypto 2> /dev/null)
+HOSTCFLAGS_sign-file.o += -I$(srctree)/tools/include/uapi/
+HOSTLDLIBS_sign-file = $(shell $(HOSTPKG_CONFIG) --libs libcrypto 2> /dev/null || echo -lcrypto)
+
+ifdef CONFIG_UNWINDER_ORC
+ifeq ($(ARCH),x86_64)
+SRCARCH := x86
+endif
+ifeq ($(ARCH),loongarch)
+SRCARCH := loongarch
+endif
+HOSTCFLAGS_sorttable.o += -I$(srctree)/tools/arch/$(SRCARCH)/include
+HOSTCFLAGS_sorttable.o += -DUNWINDER_ORC_ENABLED
+endif
+
+ifdef CONFIG_BUILDTIME_MCOUNT_SORT
+HOSTCFLAGS_sorttable.o += -DMCOUNT_SORT_ENABLED
+endif
+
+# The following programs are only built on demand
+hostprogs += unifdef gen_packed_field_checks
+
+# The module linker script is preprocessed on demand
+targets += module.lds
+
+subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
+subdir-$(CONFIG_GENKSYMS) += genksyms
+subdir-$(CONFIG_GENDWARFKSYMS) += gendwarfksyms
+subdir-$(CONFIG_SECURITY_SELINUX) += selinux
+subdir-$(CONFIG_SECURITY_IPE) += ipe
+
+# Let clean descend into subdirs
+subdir-	+= basic dtc gdb kconfig mod