On 09/20, Liao, Chang wrote: > > 在 2024/9/19 22:18, Oleg Nesterov 写道: > > On 09/19, Liao Chang wrote: > >> > >> --- a/arch/arm64/kernel/probes/uprobes.c > >> +++ b/arch/arm64/kernel/probes/uprobes.c > >> @@ -17,12 +17,16 @@ void arch_uprobe_copy_ixol(struct page *page, unsigned > >> long vaddr, > >> void *xol_page_kaddr = kmap_atomic(page); > >> void *dst = xol_page_kaddr + (vaddr & ~PAGE_MASK); > >> > >> + if (!memcmp(dst, src, len)) > >> + goto done; > > > > can't really comment, I know nothing about arm64... > > > > but don't we need to change __create_xol_area() > > > > - area->page = alloc_page(GFP_HIGHUSER); > > + area->page = alloc_page(GFP_HIGHUSER | __GFP_ZERO); > > > > to avoid the false positives? > > Indeed, it would be safer. > > Could we tolerate these false positives? Even if the page are not reset > to zero bits, if the existing bits are the same as the instruction being > copied, it still can execute the correct instruction.
OK, agreed, the task should the same data after page fault. Oleg.
