Re: [RESEND PATCH 2/2] userfaultfd: selftest: Add tests for UFFD_FREATURE_SIGBUS

[Prakash Sangappa]

On 7/26/17 7:27 AM, Andrea Arcangeli wrote:
> On Tue, Jul 25, 2017 at 12:47:42AM -0400, Prakash Sangappa wrote:
> > Signed-off-by: Prakash Sangappa <prakash.sangappa@xxxxxxxxxx>
> > ---
> >   tools/testing/selftests/vm/userfaultfd.c |  121 +++++++++++++++++++++++++++++-
> >   1 files changed, 118 insertions(+), 3 deletions(-)
> Like Mike said, some comment about the test would be better, commit
> messages are never one liners in the kernel.

Ok

> > @@ -408,6 +409,7 @@ static int copy_page(int ufd, unsigned long offset)
> >   				userfaults++;
> >   			break;
> >   		case UFFD_EVENT_FORK:
> > +			close(uffd);
> >   			uffd = msg.arg.fork.ufd;
> >   			pollfd[0].fd = uffd;
> >   			break;
> Isn't this fd leak bugfix independent of the rest of the changes? The
> only side effects should have been that it could run out of fds, but I
> assume this was found by source review as I doubt it could run out of fds.
> This could be splitted off in a separate patch.

Not just the fd leak, it causes problems here with the addition of the
new test userfaultfd_sig_test(). Since the original vma registration
persists in the parent, subsequent registration in userfaultfd_events_test()
fails with 'EBUSY' error, as userfault implementation does not allow
registering same vma with another uffd, while one exists.

Therefore, will need this change. I could just leave this fix here along
with the rest of the changes, will that be ok?

-Prakash

> Overall it looks a good test also exercising UFFD_EVENT_FORK at the
> same time.
>
> Thanks,
> Andrea