On Thu, Apr 27, 2023 at 02:17:11PM +0200, Claudio Imbrenda wrote: > > > > On Wed, Apr 26, 2023 at 03:48:34PM +0200, Claudio Imbrenda wrote: > > > > > This patch fixes a potential race in gmap_make_secure and removes the > > > > > last user of follow_page without FOLL_GET. > > > > > > > > > > Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> > > > > > Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > > > > > Fixes: 214d9bbcd3a6 ("s390/mm: provide memory management functions for protected KVM guests") > > > > > --- > > > > > arch/s390/kernel/uv.c | 32 +++++++++++--------------------- > > > > > 1 file changed, 11 insertions(+), 21 deletions(-) > > > > > > > > It would be helpful if this would be a bit more descriptive. "Fix > > > > race" is not very helpful :) > > > > > > > > What race does this fix? > > > > When can this happen? > > > > What are the consequences if the race window is being hit? > > > > > > We are locking something we don't have a reference to, and as explained > > > by Jason and David in this thread <Y9J4P/RNvY1Ztn0Q@xxxxxxxxxx> it can > > > lead to all kind of bad things, including the page getting > > > unmapped (MADV_DONTNEED), freed, reallocated as a larger folio and the > > > unlock_page() would target the wrong bit. > > > > > > Also there is another race with the FOLL_WRITE, which could race > > > between the follow_page and the get_locked_pte. > > > > > > The main point of the patch is to remove the last follow_page without > > > FOLL_GET or FOLL_PIN, removing the races can be considered a nice bonus. > > > > I've seen that discussion. What I'm actually asking for is that all of > > this information should be added to the commit description. Nobody > > will remember any of the details in one year. > > I will put it in the patch description. > > do you think the text above is enough? Fine with me. With a proper Link: tag this is much better than before. Thanks!