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/hostprogs/.gitignore | 3 +++ samples/rust/hostprogs/Makefile | 5 +++++ samples/rust/hostprogs/a.rs | 7 +++++++ samples/rust/hostprogs/b.rs | 5 +++++ samples/rust/hostprogs/single.rs | 12 ++++++++++++ 5 files changed, 32 insertions(+) create mode 100644 samples/rust/hostprogs/.gitignore create mode 100644 samples/rust/hostprogs/Makefile create mode 100644 samples/rust/hostprogs/a.rs create mode 100644 samples/rust/hostprogs/b.rs create mode 100644 samples/rust/hostprogs/single.rs (limited to 'samples/rust/hostprogs') diff --git a/samples/rust/hostprogs/.gitignore b/samples/rust/hostprogs/.gitignore new file mode 100644 index 000000000..a6c173da5 --- /dev/null +++ b/samples/rust/hostprogs/.gitignore @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0 + +single diff --git a/samples/rust/hostprogs/Makefile b/samples/rust/hostprogs/Makefile new file mode 100644 index 000000000..8ddcbd741 --- /dev/null +++ b/samples/rust/hostprogs/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 + +hostprogs-always-y := single + +single-rust := y diff --git a/samples/rust/hostprogs/a.rs b/samples/rust/hostprogs/a.rs new file mode 100644 index 000000000..f7a4a3d0f --- /dev/null +++ b/samples/rust/hostprogs/a.rs @@ -0,0 +1,7 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Rust single host program sample: module `a`. + +pub(crate) fn f(x: i32) { + println!("The number is {}.", x); +} diff --git a/samples/rust/hostprogs/b.rs b/samples/rust/hostprogs/b.rs new file mode 100644 index 000000000..c16758906 --- /dev/null +++ b/samples/rust/hostprogs/b.rs @@ -0,0 +1,5 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Rust single host program sample: module `b`. + +pub(crate) const CONSTANT: i32 = 42; diff --git a/samples/rust/hostprogs/single.rs b/samples/rust/hostprogs/single.rs new file mode 100644 index 000000000..8c48a1193 --- /dev/null +++ b/samples/rust/hostprogs/single.rs @@ -0,0 +1,12 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Rust single host program sample. + +mod a; +mod b; + +fn main() { + println!("Hello world!"); + + a::f(b::CONSTANT); +} -- cgit v1.3.1