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, 192 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-netdev b/Documentation/ABI/testing/sysfs-class-led-trigger-netdev
new file mode 100644
index 000000000..ed46b37ab
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-led-trigger-netdev
@@ -0,0 +1,192 @@
+What:		/sys/class/leds/<led>/device_name
+Date:		Dec 2017
+KernelVersion:	4.16
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Specifies the network device name to monitor.
+
+What:		/sys/class/leds/<led>/interval
+Date:		Dec 2017
+KernelVersion:	4.16
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Specifies the duration of the LED blink in milliseconds.
+		Defaults to 50 ms.
+
+		When offloaded is true, the interval value MUST be set to the
+		default value and cannot be changed.
+		Trying to set any value in this specific mode will return
+		an EINVAL error.
+
+What:		/sys/class/leds/<led>/link
+Date:		Dec 2017
+KernelVersion:	4.16
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal the link state of the named network device.
+
+		If set to 0 (default), the LED's normal state is off.
+
+		If set to 1, the LED's normal state reflects the link state
+		of the named network device.
+		Setting this value also immediately changes the LED state.
+
+
+What:		/sys/class/leds/<led>/tx
+Date:		Dec 2017
+KernelVersion:	4.16
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal transmission of data on the named network device.
+
+		If set to 0 (default), the LED will not blink on transmission.
+
+		If set to 1, the LED will blink for the milliseconds specified
+		in interval to signal transmission.
+
+		When offloaded is true, the blink interval is controlled by
+		hardware and won't reflect the value set in interval.
+
+What:		/sys/class/leds/<led>/rx
+Date:		Dec 2017
+KernelVersion:	4.16
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal reception of data on the named network device.
+
+		If set to 0 (default), the LED will not blink on reception.
+
+		If set to 1, the LED will blink for the milliseconds specified
+		in interval to signal reception.
+
+		When offloaded is true, the blink interval is controlled by
+		hardware and won't reflect the value set in interval.
+
+What:		/sys/class/leds/<led>/offloaded
+Date:		Jun 2023
+KernelVersion:	6.5
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Communicate whether the LED trigger modes are offloaded to
+		hardware or whether software fallback is used.
+
+		If 0, the LED is using software fallback to blink.
+
+		If 1, the LED blinking in requested mode is offloaded to
+		hardware.
+
+What:		/sys/class/leds/<led>/link_10
+Date:		Jun 2023
+KernelVersion:	6.5
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal the link speed state of 10Mbps of the named network device.
+
+		If set to 0 (default), the LED's normal state is off.
+
+		If set to 1, the LED's normal state reflects the link state
+		speed of 10MBps of the named network device.
+		Setting this value also immediately changes the LED state.
+
+		Present only if the named network device supports 10Mbps link speed.
+
+What:		/sys/class/leds/<led>/link_100
+Date:		Jun 2023
+KernelVersion:	6.5
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal the link speed state of 100Mbps of the named network device.
+
+		If set to 0 (default), the LED's normal state is off.
+
+		If set to 1, the LED's normal state reflects the link state
+		speed of 100Mbps of the named network device.
+		Setting this value also immediately changes the LED state.
+
+		Present only if the named network device supports 100Mbps link speed.
+
+What:		/sys/class/leds/<led>/link_1000
+Date:		Jun 2023
+KernelVersion:	6.5
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal the link speed state of 1000Mbps of the named network device.
+
+		If set to 0 (default), the LED's normal state is off.
+
+		If set to 1, the LED's normal state reflects the link state
+		speed of 1000Mbps of the named network device.
+		Setting this value also immediately changes the LED state.
+
+		Present only if the named network device supports 1000Mbps link speed.
+
+What:		/sys/class/leds/<led>/link_2500
+Date:		Nov 2023
+KernelVersion:	6.8
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal the link speed state of 2500Mbps of the named network device.
+
+		If set to 0 (default), the LED's normal state is off.
+
+		If set to 1, the LED's normal state reflects the link state
+		speed of 2500Mbps of the named network device.
+		Setting this value also immediately changes the LED state.
+
+		Present only if the named network device supports 2500Mbps link speed.
+
+What:		/sys/class/leds/<led>/link_5000
+Date:		Nov 2023
+KernelVersion:	6.8
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal the link speed state of 5000Mbps of the named network device.
+
+		If set to 0 (default), the LED's normal state is off.
+
+		If set to 1, the LED's normal state reflects the link state
+		speed of 5000Mbps of the named network device.
+		Setting this value also immediately changes the LED state.
+
+		Present only if the named network device supports 5000Mbps link speed.
+
+What:		/sys/class/leds/<led>/link_10000
+Date:		Nov 2023
+KernelVersion:	6.8
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal the link speed state of 10000Mbps of the named network device.
+
+		If set to 0 (default), the LED's normal state is off.
+
+		If set to 1, the LED's normal state reflects the link state
+		speed of 10000Mbps of the named network device.
+		Setting this value also immediately changes the LED state.
+
+		Present only if the named network device supports 10000Mbps link speed.
+
+What:		/sys/class/leds/<led>/half_duplex
+Date:		Jun 2023
+KernelVersion:	6.5
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal the link half duplex state of the named network device.
+
+		If set to 0 (default), the LED's normal state is off.
+
+		If set to 1, the LED's normal state reflects the link half
+		duplex state of the named network device.
+		Setting this value also immediately changes the LED state.
+
+What:		/sys/class/leds/<led>/full_duplex
+Date:		Jun 2023
+KernelVersion:	6.5
+Contact:	linux-leds@vger.kernel.org
+Description:
+		Signal the link full duplex state of the named network device.
+
+		If set to 0 (default), the LED's normal state is off.
+
+		If set to 1, the LED's normal state reflects the link full
+		duplex state of the named network device.
+		Setting this value also immediately changes the LED state.