On Fri, Oct 18, 2019 at 11:43:01AM +0200, glider@xxxxxxxxxx wrote: > When data is copied to memory from a device KMSAN should treat it as > initialized. In most cases it's enough to just unpoison the buffer that > is known to come from a device. > In the case with __do_page_cache_readahead() and bio_copy_user_iov() we > have to mark the whole pages as ignored by KMSAN, as it's not obvious > where these pages are read again. ... > +++ b/mm/filemap.c > @@ -18,6 +18,7 @@ > #include <linux/uaccess.h> > #include <linux/capability.h> > #include <linux/kernel_stat.h> > +#include <linux/kmsan-checks.h> > #include <linux/gfp.h> > #include <linux/mm.h> > #include <linux/swap.h> > @@ -2810,6 +2811,8 @@ static struct page *do_read_cache_page(struct address_space *mapping, > page = wait_on_page_read(page); > if (IS_ERR(page)) > return page; > + /* Assume all pages in page cache are initialized. */ > + kmsan_unpoison_shadow(page_address(page), PAGE_SIZE); Why would you do that? The page cache already keeps track of which pages are initialised -- the PageUptodate flag is set on them. Indeed, just adding a kmsan call to SetPageUptodate and __SetPageUptodate would probably be a very straightforward way of handling things, and probably means you can get rid of a lot of these other calls.
