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, 66 insertions, 0 deletions

diff --git a/Documentation/usb/linux.inf b/Documentation/usb/linux.inf
new file mode 100644
index 000000000..c569ac6be
--- /dev/null
+++ b/Documentation/usb/linux.inf
@@ -0,0 +1,66 @@
+; Based on template INF file found at
+;    <https://msdn.microsoft.com/en-us/library/ff570620.aspx>
+; which was:
+;    Copyright (c) Microsoft Corporation
+; and released under the MLPL as found at:
+;    <http://msdn.microsoft.com/en-us/cc300389.aspx#MLPL>.
+; For use only on Windows operating systems.
+
+[Version]
+Signature           = "$Windows NT$"
+Class               = Net
+ClassGUID           = {4d36e972-e325-11ce-bfc1-08002be10318}
+Provider            = %Linux%
+DriverVer           = 06/21/2006,6.0.6000.16384
+
+[Manufacturer]
+%Linux%             = LinuxDevices,NTx86,NTamd64,NTia64
+
+; Decoration for x86 architecture
+[LinuxDevices.NTx86]
+%LinuxDevice%       = RNDIS.NT.5.1, USB\VID_0525&PID_a4a2, USB\VID_1d6b&PID_0104&MI_00
+
+; Decoration for x64 architecture
+[LinuxDevices.NTamd64]
+%LinuxDevice%       = RNDIS.NT.5.1, USB\VID_0525&PID_a4a2, USB\VID_1d6b&PID_0104&MI_00
+
+; Decoration for ia64 architecture
+[LinuxDevices.NTia64]
+%LinuxDevice%       = RNDIS.NT.5.1, USB\VID_0525&PID_a4a2, USB\VID_1d6b&PID_0104&MI_00
+
+;@@@ This is the common setting for setup
+[ControlFlags]
+ExcludeFromSelect=*
+
+; DDInstall section
+; References the in-build Netrndis.inf
+[RNDIS.NT.5.1]
+Characteristics     = 0x84   ; NCF_PHYSICAL + NCF_HAS_UI
+BusType             = 15
+; NEVER REMOVE THE FOLLOWING REFERENCE FOR NETRNDIS.INF
+include             = netrndis.inf
+needs               = Usb_Rndis.ndi
+AddReg              = Rndis_AddReg_Vista
+
+; DDInstal.Services section
+[RNDIS.NT.5.1.Services]
+include             = netrndis.inf
+needs               = Usb_Rndis.ndi.Services
+
+; Optional registry settings. You can modify as needed.
+[RNDIS_AddReg_Vista]
+HKR, NDI\params\VistaProperty, ParamDesc,  0, %Vista_Property%
+HKR, NDI\params\VistaProperty, type,       0, "edit"
+HKR, NDI\params\VistaProperty, LimitText,  0, "12"
+HKR, NDI\params\VistaProperty, UpperCase,  0, "1"
+HKR, NDI\params\VistaProperty, default,    0, " "
+HKR, NDI\params\VistaProperty, optional,   0, "1"
+
+; No sys copyfiles - the sys files are already in-build
+; (part of the operating system).
+; We do not support XP SP1-, 2003 SP1-, ME, 9x.
+
+[Strings]
+Linux                 = "Linux Developer Community"
+LinuxDevice           = "Linux USB Ethernet/RNDIS Gadget"
+Vista_Property        = "Optional Vista Property"