[Bug report] hash_name() may cross page boundary and trigger sleep in RCU context

[Al Viro]

On Wed, Nov 26, 2025 at 05:05:05PM +0800, Zizhi Wo wrote:

> under an RCU read-side critical section. In linux-mainline, arm/arm64
> do_page_fault() still has this problem:
> 
> lock_mm_and_find_vma->get_mmap_lock_carefully->mmap_read_lock_killable.

	arm64 shouldn't hit do_page_fault() in the first place, and
do_translation_fault() there will see that address is beyond TASK_SIZE
and go straight to do_bad_area() -> __do_kernel_fault() -> fixup_exception(),
with no messing with mmap_lock.

	Can anybody confirm that problem exists on arm64 (ideally - with
reproducer)?