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 --- Documentation/ABI/testing/debugfs-hyperv | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) create mode 100644 Documentation/ABI/testing/debugfs-hyperv (limited to 'Documentation/ABI/testing/debugfs-hyperv') diff --git a/Documentation/ABI/testing/debugfs-hyperv b/Documentation/ABI/testing/debugfs-hyperv new file mode 100644 index 000000000..9185e1b06 --- /dev/null +++ b/Documentation/ABI/testing/debugfs-hyperv @@ -0,0 +1,23 @@ +What: /sys/kernel/debug/hyperv//fuzz_test_state +Date: October 2019 +KernelVersion: 5.5 +Contact: Branden Bonaby +Description: Fuzz testing status of a vmbus device, whether its in an ON + state or a OFF state +Users: Debugging tools + +What: /sys/kernel/debug/hyperv//delay/fuzz_test_buffer_interrupt_delay +Date: October 2019 +KernelVersion: 5.5 +Contact: Branden Bonaby +Description: Fuzz testing buffer interrupt delay value between 0 - 1000 + microseconds (inclusive). +Users: Debugging tools + +What: /sys/kernel/debug/hyperv//delay/fuzz_test_message_delay +Date: October 2019 +KernelVersion: 5.5 +Contact: Branden Bonaby +Description: Fuzz testing message delay value between 0 - 1000 microseconds + (inclusive). +Users: Debugging tools -- cgit v1.3.1