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, 34 insertions, 0 deletions

diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
new file mode 100644
index 000000000..7b6dd53e8
--- /dev/null
+++ b/drivers/mtd/Makefile
@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the memory technology device drivers.
+#
+
+# Core functionality.
+obj-$(CONFIG_MTD)		+= mtd.o
+mtd-y				:= mtdcore.o mtdsuper.o mtdconcat.o mtdpart.o mtdchar.o
+mtd-$(CONFIG_MTD_VIRT_CONCAT)	+= mtd_virt_concat.o
+
+obj-y				+= parsers/
+
+# 'Users' - code which presents functionality to userspace.
+obj-$(CONFIG_MTD_BLKDEVS)	+= mtd_blkdevs.o
+obj-$(CONFIG_MTD_BLOCK)		+= mtdblock.o
+obj-$(CONFIG_MTD_BLOCK_RO)	+= mtdblock_ro.o
+obj-$(CONFIG_FTL)		+= ftl.o
+obj-$(CONFIG_NFTL)		+= nftl.o
+obj-$(CONFIG_INFTL)		+= inftl.o
+obj-$(CONFIG_RFD_FTL)		+= rfd_ftl.o
+obj-$(CONFIG_SSFDC)		+= ssfdc.o
+obj-$(CONFIG_SM_FTL)		+= sm_ftl.o
+obj-$(CONFIG_MTD_OOPS)		+= mtdoops.o
+obj-$(CONFIG_MTD_PSTORE)	+= mtdpstore.o
+obj-$(CONFIG_MTD_SWAP)		+= mtdswap.o
+
+nftl-objs		:= nftlcore.o nftlmount.o
+inftl-objs		:= inftlcore.o inftlmount.o
+
+obj-y		+= chips/ lpddr/ maps/ devices/ nand/ tests/
+
+obj-$(CONFIG_MTD_SPI_NOR)	+= spi-nor/
+obj-$(CONFIG_MTD_UBI)		+= ubi/
+obj-$(CONFIG_MTD_HYPERBUS)	+= hyperbus/