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, 36 insertions, 0 deletions

diff --git a/drivers/mtd/maps/Makefile b/drivers/mtd/maps/Makefile
new file mode 100644
index 000000000..fbed27815
--- /dev/null
+++ b/drivers/mtd/maps/Makefile
@@ -0,0 +1,36 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# linux/drivers/maps/Makefile
+#
+
+ifeq ($(CONFIG_MTD_COMPLEX_MAPPINGS),y)
+obj-$(CONFIG_MTD)		+= map_funcs.o
+endif
+
+# Chip mappings
+obj-$(CONFIG_MTD_CFI_FLAGADM)	+= cfi_flagadm.o
+obj-$(CONFIG_MTD_DC21285)	+= dc21285.o
+obj-$(CONFIG_MTD_L440GX)	+= l440gx.o
+obj-$(CONFIG_MTD_AMD76XROM)	+= amd76xrom.o
+obj-$(CONFIG_MTD_ESB2ROM)	+= esb2rom.o
+obj-$(CONFIG_MTD_ICHXROM)	+= ichxrom.o
+obj-$(CONFIG_MTD_CK804XROM)	+= ck804xrom.o
+obj-$(CONFIG_MTD_TSUNAMI)	+= tsunami_flash.o
+obj-$(CONFIG_MTD_PXA2XX)	+= pxa2xx-flash.o
+obj-$(CONFIG_MTD_PHYSMAP)	+= physmap.o
+physmap-y			:= physmap-core.o
+physmap-$(CONFIG_MTD_PHYSMAP_VERSATILE) += physmap-versatile.o
+physmap-$(CONFIG_MTD_PHYSMAP_GEMINI) += physmap-gemini.o
+physmap-$(CONFIG_MTD_PHYSMAP_IXP4XX) += physmap-ixp4xx.o
+obj-$(CONFIG_MTD_PISMO)		+= pismo.o
+obj-$(CONFIG_MTD_PCMCIA)	+= pcmciamtd.o
+obj-$(CONFIG_MTD_SA1100)	+= sa1100-flash.o
+obj-$(CONFIG_MTD_SBC_GXX)	+= sbc_gxx.o
+obj-$(CONFIG_MTD_SUN_UFLASH)	+= sun_uflash.o
+obj-$(CONFIG_MTD_SCx200_DOCFLASH)+= scx200_docflash.o
+obj-$(CONFIG_MTD_SOLUTIONENGINE)+= solutionengine.o
+obj-$(CONFIG_MTD_PCI)		+= pci.o
+obj-$(CONFIG_MTD_SCB2_FLASH)	+= scb2_flash.o
+obj-$(CONFIG_MTD_PLATRAM)	+= plat-ram.o
+obj-$(CONFIG_MTD_VMU)		+= vmu-flash.o
+obj-$(CONFIG_MTD_LANTIQ)	+= lantiq-flash.o