Re: [PATCHv2 bpf-next] selftests/bpf: Fix d_path test

Song Liu
2023-09-05T18:40:55Z

On Mon, Sep 4, 2023 at 12:10 AM Jiri Olsa <olsajiri@gmail.com> wrote:
>
> On Fri, Sep 01, 2023 at 04:09:31PM -0700, Song Liu wrote:
> > On Thu, Aug 31, 2023 at 8:21 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
> > >
> > > On 8/31/23 4:11 PM, Jiri Olsa wrote:
> > > > Recent commit [1] broken d_path test, because now filp_close is not called
> > > > directly from sys_close, but eventually later when the file is finally
> > > > released.
> > > >
> > > > As suggested by Hou Tao we don't need to re-hook the bpf program, but just
> > > > instead we can use sys_close_range to trigger filp_close synchronously.
> > > >
> > > > [1] 021a160abf62 ("fs: use __fput_sync in close(2)")
> > > > Suggested-by: Hou Tao <houtao@huaweicloud.com>
> > > > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > >
> > > That did the trick, thanks everyone, applied!
> >
> > I guess I am a bit late. But how about we use something like the following?
> > I like this one better because it tests bpf_d_path() from retval at fexit.
>
> right, that would have been an option as well
>
> >
> > Thanks,
> > Song
> >
> >
> >
> >
> > diff --git i/kernel/trace/bpf_trace.c w/kernel/trace/bpf_trace.c
> > index a7264b2c17ad..fe91836cedcd 100644
> > --- i/kernel/trace/bpf_trace.c
> > +++ w/kernel/trace/bpf_trace.c
> > @@ -941,6 +941,7 @@ BTF_ID(func, vfs_fallocate)
> > BTF_ID(func, dentry_open)
> > BTF_ID(func, vfs_getattr)
> > BTF_ID(func, filp_close)
> > +BTF_ID(func, close_fd_get_file)
>
> I liked using the close_range syscall because we did not need to
> add new allowed function.. however close_fd_get_file looks safe
> enough so I wouldn't mind changing that if you insist ;-)

Let's use close_range() then. I will send another patch to test
something with "struct file *" as retval on fexit.

Thanks,
Song