On Wed, May 02, 2018 at 07:25:17PM +0200, Andrey Konovalov wrote: > On Wed, May 2, 2018 at 5:36 PM, Kirill A. Shutemov > <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > > On Wed, May 02, 2018 at 02:38:42PM +0000, Andrey Konovalov wrote: > >> > Does having a tagged address here makes any difference? I couldn't hit a > >> > failure with my simple tests (LD_PRELOAD a library that randomly adds > >> > tags to pointers returned by malloc). > >> > >> I think you're right, follow_page_mask is only called from > >> __get_user_pages, which already untagged the address. I'll remove > >> untagging here. > > > > It also called from follow_page(). Have you covered all its callers? > > Oh, missed that, will take a look. > > Thinking about that, would it make sense to add untagging to find_vma > (and others) instead of trying to cover all find_vma callers? I don't think adding the untagging to find_vma() is sufficient. In many cases the caller does a subsequent check like 'start < vma->vm_start' (see sys_msync() as an example, there are a few others as well). What I did in my tests was a WARN_ON_ONCE() in find_vma() if the address is tagged. -- Catalin
