On Wed 22-02-17 14:39:24, Minchan Kim wrote: > With rw_page, page_endio is used for completing IO on a page > and it propagates write error to the address space if the IO > fails. The problem is it accesses page->mapping directly which > might be okay for file-backed pages but it shouldn't for > anonymous page. Otherwise, it can corrupt one of field from > anon_vma under us and system goes panic randomly.
I was about to say that anonymous pages shouldn't hit that path because the end_swap_bio_write doesn call page_endio. But then I've noticed that zram does call this function. On a closer look, though, it doesn't seem to call it with err != 0 so it cannot hit this path. So I am wondering whether this actually fixes anything. Why it has been marked for stable? > > Cc: Matthew Wilcox <[email protected]> > Cc: <[email protected]> > Signed-off-by: Minchan Kim <[email protected]> > --- > mm/filemap.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index 2ba46f410c7c..1944c631e3e6 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1008,9 +1008,12 @@ void page_endio(struct page *page, bool is_write, int > err) > unlock_page(page); > } else { > if (err) { > + struct address_space *mapping; > + > SetPageError(page); > - if (page->mapping) > - mapping_set_error(page->mapping, err); > + mapping = page_mapping(page); > + if (mapping) > + mapping_set_error(mapping, err); > } > end_page_writeback(page); > } > -- > 2.7.4 -- Michal Hocko SUSE Labs
