> Changing the bits requires holding inode->i_mutex, so it cannot be done > during the page fault (due to mmap_sem being held during the fault). We > could do this during vm_mmap_pgoff, but that would need coverage in > mprotect as well, but to check for MAP_SHARED, we'd need to hold mmap_sem > again. We could clear at open() time, but it's possible things are > accidentally opening with O_RDWR and only reading. Better to clear on > close and error failures (i.e. an improvement over now, which is not > clearing at all). > > Instead, detect the need to clear the bits during the page fault, and > actually remove the bits during final fput. Since the file was open for > writing, it wouldn't have been possible to execute it yet. > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > --- > I think this is the best we can do; everything else is blocked by mmap_sem. It should be done at mmap time, before even taking mmap_sem. Adding a new field for this to strut file isn't really acceptable. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
