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 --- rust/helpers/bitmap.c | 10 ++++++++++ 1 file changed, 10 insertions(+) create mode 100644 rust/helpers/bitmap.c (limited to 'rust/helpers/bitmap.c') diff --git a/rust/helpers/bitmap.c b/rust/helpers/bitmap.c new file mode 100644 index 000000000..e4e9f4361 --- /dev/null +++ b/rust/helpers/bitmap.c @@ -0,0 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +__rust_helper +void rust_helper_bitmap_copy_and_extend(unsigned long *to, const unsigned long *from, + unsigned int count, unsigned int size) +{ + bitmap_copy_and_extend(to, from, count, size); +} -- cgit v1.3.1