| Message ID | 20230517190916.3429499-2-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/uffd: Fix vma merge/split | expand |
On Wed, 17 May 2023 15:09:15 -0400 Peter Xu <peterx@redhat.com> 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@FVFF77S0Q05N.cambridge.arm.com/ > > 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@gmail.com> > Cc: Mike Rapoport (IBM) <rppt@kernel.org> > Cc: Liam R. Howlett <Liam.Howlett@oracle.com> > Reported-by: Mark Rutland <mark.rutland@arm.com> > Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com> > Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com> > 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?
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@redhat.com> 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@FVFF77S0Q05N.cambridge.arm.com/ > > > > 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@gmail.com> > > Cc: Mike Rapoport (IBM) <rppt@kernel.org> > > Cc: Liam R. Howlett <Liam.Howlett@oracle.com> > > Reported-by: Mark Rutland <mark.rutland@arm.com> > > Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com> > > Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com> > > 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,
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 0fd96d6e39ce..17c8c345dac4 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1459,6 +1459,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, vma_iter_set(&vmi, start); prev = vma_prev(&vmi); + if (vma->vm_start < start) + prev = vma; ret = 0; for_each_vma_range(vmi, vma, end) { @@ -1625,6 +1627,9 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, vma_iter_set(&vmi, start); prev = vma_prev(&vmi); + if (vma->vm_start < start) + prev = vma; + ret = 0; for_each_vma_range(vmi, vma, end) { cond_resched();