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, 50 insertions, 0 deletions

diff --git a/arch/powerpc/sysdev/Makefile b/arch/powerpc/sysdev/Makefile
new file mode 100644
index 000000000..0834a9a12
--- /dev/null
+++ b/arch/powerpc/sysdev/Makefile
@@ -0,0 +1,50 @@
+# SPDX-License-Identifier: GPL-2.0
+
+mpic-msi-obj-$(CONFIG_PCI_MSI)	+= mpic_msi.o mpic_u3msi.o
+obj-$(CONFIG_MPIC)		+= mpic.o $(mpic-msi-obj-y)
+obj-$(CONFIG_MPIC_TIMER)        += mpic_timer.o
+obj-$(CONFIG_FSL_MPIC_TIMER_WAKEUP)	+= fsl_mpic_timer_wakeup.o
+mpic-msgr-obj-$(CONFIG_MPIC_MSGR)	+= mpic_msgr.o
+obj-$(CONFIG_MPIC)		+= mpic.o $(mpic-msi-obj-y) $(mpic-msgr-obj-y)
+obj-$(CONFIG_PPC_EPAPR_HV_PIC)	+= ehv_pic.o
+fsl-msi-obj-$(CONFIG_PCI_MSI)	+= fsl_msi.o
+obj-$(CONFIG_PPC_MSI_BITMAP)	+= msi_bitmap.o
+
+obj-$(CONFIG_PPC_MPC106)	+= grackle.o
+obj-$(CONFIG_PPC_DCR_NATIVE)	+= dcr-low.o
+obj-$(CONFIG_U3_DART)		+= dart_iommu.o
+obj-$(CONFIG_MMIO_NVRAM)	+= mmio_nvram.o
+obj-$(CONFIG_FSL_SOC)		+= fsl_soc.o fsl_mpic_err.o
+obj-$(CONFIG_FSL_PCI)		+= fsl_pci.o $(fsl-msi-obj-y)
+obj-$(CONFIG_FSL_PMC)		+= fsl_pmc.o
+obj-$(CONFIG_FSL_CORENET_RCPM)	+= fsl_rcpm.o
+obj-$(CONFIG_FSL_LBC)		+= fsl_lbc.o
+obj-$(CONFIG_FSL_GTM)		+= fsl_gtm.o
+obj-$(CONFIG_FSL_RIO)		+= fsl_rio.o fsl_rmu.o
+obj-$(CONFIG_TSI108_BRIDGE)	+= tsi108_pci.o tsi108_dev.o
+obj-$(CONFIG_RTC_DRV_CMOS)	+= rtc_cmos_setup.o
+
+obj-$(CONFIG_PPC_INDIRECT_PCI)	+= indirect_pci.o
+obj-$(CONFIG_PPC_I8259)		+= i8259.o
+obj-$(CONFIG_IPIC)		+= ipic.o
+obj-$(CONFIG_OF_RTC)		+= of_rtc.o
+
+obj-$(CONFIG_CPM)		+= cpm_common.o
+obj-$(CONFIG_CPM2)		+= cpm2.o cpm2_pic.o cpm_gpio.o
+obj-$(CONFIG_8xx_GPIO)		+= cpm_gpio.o
+obj-$(CONFIG_QUICC_ENGINE)	+= cpm_common.o
+obj-$(CONFIG_PPC_DCR)		+= dcr.o
+
+obj-$(CONFIG_PPC_MPC512x)	+= mpc5xxx_clocks.o
+obj-$(CONFIG_PPC_MPC52xx)	+= mpc5xxx_clocks.o
+
+ifdef CONFIG_SUSPEND
+obj-$(CONFIG_PPC_BOOK3S_32)	+= 6xx-suspend.o
+endif
+
+obj-$(CONFIG_PPC_EARLY_DEBUG_MEMCONS)	+= udbg_memcons.o
+
+obj-$(CONFIG_PPC_XICS)		+= xics/
+obj-$(CONFIG_PPC_XIVE)		+= xive/
+
+obj-$(CONFIG_GE_FPGA)		+= ge/