From 1039bffd6ae9c75b42b7d148d6c1106134107b66 Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Tue, 28 Jul 2026 03:16:42 +0100 Subject: ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults 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 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) Reviewed-by: Linus Walleij Signed-off-by: Qi Xi Signed-off-by: Xie Yuanbin Signed-off-by: Russell King --- .../ABI/testing/sysfs-class-led-trigger-pattern | 50 ++++++++++++++++++++++ 1 file changed, 50 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-led-trigger-pattern (limited to 'Documentation/ABI/testing/sysfs-class-led-trigger-pattern') diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-pattern b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern new file mode 100644 index 000000000..22f28f2e9 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern @@ -0,0 +1,50 @@ +What: /sys/class/leds//pattern +Date: September 2018 +KernelVersion: 4.20 +Description: + Specify a software pattern for the LED, that supports altering + the brightness for the specified duration with one software + timer. It can do gradual dimming and step change of brightness. + + The pattern is given by a series of tuples, of brightness and + duration (ms). + + The exact format is described in: + Documentation/devicetree/bindings/leds/leds-trigger-pattern.txt + +What: /sys/class/leds//hr_pattern +Date: April 2024 +Description: + Specify a software pattern for the LED, that supports altering + the brightness for the specified duration with one software + timer. It can do gradual dimming and step change of brightness. + + Unlike the /sys/class/leds//pattern, this attribute runs + a pattern on high-resolution timer (hrtimer). + +What: /sys/class/leds//hw_pattern +Date: September 2018 +KernelVersion: 4.20 +Description: + Specify a hardware pattern for the LED, for LED hardware that + supports autonomously controlling brightness over time, according + to some preprogrammed hardware patterns. It deactivates any active + software pattern. + + Since different LED hardware can have different semantics of + hardware patterns, each driver is expected to provide its own + description for the hardware patterns in their documentation + file at Documentation/leds/. + +What: /sys/class/leds//repeat +Date: September 2018 +KernelVersion: 4.20 +Description: + Specify a pattern repeat number. -1 means repeat indefinitely, + other negative numbers and number 0 are invalid. + + This file will always return the originally written repeat + number. + + It should be noticed that some leds, like EL15203000 may + only support indefinitely patterns, so they always store -1. -- cgit v1.3.1