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 --- samples/rust/rust_minimal.rs | 48 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 samples/rust/rust_minimal.rs (limited to 'samples/rust/rust_minimal.rs') diff --git a/samples/rust/rust_minimal.rs b/samples/rust/rust_minimal.rs new file mode 100644 index 000000000..8eb958357 --- /dev/null +++ b/samples/rust/rust_minimal.rs @@ -0,0 +1,48 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Rust minimal sample. + +use kernel::prelude::*; + +module! { + type: RustMinimal, + name: "rust_minimal", + authors: ["Rust for Linux Contributors"], + description: "Rust minimal sample", + license: "GPL", + params: { + test_parameter: i64 { + default: 1, + description: "This parameter has a default of 1", + }, + }, +} + +struct RustMinimal { + numbers: KVec, +} + +impl kernel::Module for RustMinimal { + fn init(_module: &'static ThisModule) -> Result { + pr_info!("Rust minimal sample (init)\n"); + pr_info!("Am I built-in? {}\n", !cfg!(MODULE)); + pr_info!( + "test_parameter: {}\n", + *module_parameters::test_parameter.value() + ); + + let mut numbers = KVec::new(); + numbers.push(72, GFP_KERNEL)?; + numbers.push(108, GFP_KERNEL)?; + numbers.push(200, GFP_KERNEL)?; + + Ok(RustMinimal { numbers }) + } +} + +impl Drop for RustMinimal { + fn drop(&mut self) { + pr_info!("My numbers are {:?}\n", self.numbers); + pr_info!("Rust minimal sample (exit)\n"); + } +} -- cgit v1.3.1