On Fri, 25 Sep 2026 09:36:26 +0200, David Hildenbrand (Arm) wrote: > It would also be helpful to describe if this was actually hit in practice so > far. IOW, how relevant is this in practice.
Not that I know of. An LLM found it reading the code, and I couldn't find a report of it on linux-mm or lkml. > Will this trigger a kernel splat later? Yes, with CONFIG_PAGE_TABLE_CHECK. When the moved page is faulted in at the destination, do_swap_page() copies the uffd bit to the present PTE and, because the destination isn't WP-registered, also makes it writable. A read fault is enough: WARNING: mm/page_table_check.c:202 at __page_table_check_ptes_set+0x185/0x1e0 Call Trace: set_ptes+0x67/0xc0 do_swap_page+0x990/0xfe0 __handle_mm_fault+0x7d0/0xeb0 handle_mm_fault+0x9c/0x250 do_user_addr_fault+0x207/0x650 exc_page_fault+0x65/0x150 asm_exc_page_fault+0x26/0x30 That's on 7.3-rc4 in QEMU, from a WP- or RWP-armed source; with this patch applied it doesn't fire. I'll put it in the v3 changelog. Thanks, Donggeun
