On Thu, Dec 10, 2015 at 11:33 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Thu, Dec 10, 2015 at 07:16:11PM +0100, Willy Tarreau wrote: > >> > Is f_flags safe to write like this without holding a lock? >> >> Unfortunately I have no idea. I've seen places where it's written without >> taking a lock such as in blkdev_open() and I don't think that this one is >> called with a lock held. > > In any ->open() we obviously have nobody else able to find that struct file, > let alone modify it, so there the damn thing is essentially caller-private > and no locking is needed. In open, sure, but what about under mm/memory.c where we're trying to twiddle it from vma->file->f_flags as in my patch? That seemed like it would want atomic safety. -Kees -- Kees Cook Chrome OS & Brillo Security -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>