On Wed, May 17, 2023 at 01:23:21PM -0700, Andrew Morton wrote: > On Wed, 17 May 2023 15:09:15 -0400 Peter Xu <peterx@xxxxxxxxxx> wrote: > > > It seems vma merging with uffd paths is broken with either > > register/unregister, where right now we can feed wrong parameters to > > vma_merge() and it's found by recent patch which moved asserts upwards in > > vma_merge() by Lorenzo Stoakes: > > > > https://lore.kernel.org/all/ZFunF7DmMdK05MoF@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > > > It's possible that "start" is contained within vma but not clamped to its > > start. We need to convert this into either "cannot merge" case or "can > > merge" case 4 which permits subdivision of prev by assigning vma to > > prev. As we loop, each subsequent VMA will be clamped to the start. > > > > This patch will eliminate the report and make sure vma_merge() calls will > > become legal again. > > > > One thing to mention is that the "Fixes: 29417d292bd0" below is there only > > to help explain where the warning can start to trigger, the real commit to > > fix should be 69dbe6daf104. Commit 29417d292bd0 helps us to identify the > > issue, but unfortunately we may want to keep it in Fixes too just to ease > > kernel backporters for easier tracking. > > > > Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx> > > Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx> > > Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > > Reported-by: Mark Rutland <mark.rutland@xxxxxxx> > > Reviewed-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx> > > Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > > Fixes: 29417d292bd0 ("mm/mmap/vma_merge: always check invariants") > > Fixes: 69dbe6daf104 ("userfaultfd: use maple tree iterator to iterate VMAs") > > I don't know how -stable maintainers are to handle more than a single > Fixes: target, given that Fixes: means "kernels which have that patch > need this one". Can we narrow this down to a single commit for this > purpose? Please just keep: Fixes: 69dbe6daf104 ("userfaultfd: use maple tree iterator to iterate VMAs") I just noticed 29417d292bd0 is only in rc1 so no backport needed anyway. We definitely need 69dbe6daf104 marked Fixes for backport till 6.1+. Thanks, -- Peter Xu
