Re: [patch net-next] selftests: bpf: don't try to read files without read permission

[Jakub Kicinski <jakub.kicinski@netronome.com>]

On Thu, 31 Oct 2019 16:35:35 -0700, Jakub Kicinski wrote:
> On Tue, 15 Oct 2019 12:00:56 +0200, Jiri Pirko wrote:
> > From: Jiri Pirko <jiri@mellanox.com>
> > 
> > Recently couple of files that are write only were added to netdevsim
> > debugfs. Don't read these files and avoid error.
> > 
> > Reported-by: kernel test robot <rong.a.chen@intel.com>
> > Signed-off-by: Jiri Pirko <jiri@mellanox.com>
> > ---
> >  tools/testing/selftests/bpf/test_offload.py | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/testing/selftests/bpf/test_offload.py b/tools/testing/selftests/bpf/test_offload.py
> > index 15a666329a34..c44c650bde3a 100755
> > --- a/tools/testing/selftests/bpf/test_offload.py
> > +++ b/tools/testing/selftests/bpf/test_offload.py
> > @@ -312,7 +312,7 @@ class DebugfsDir:
> >              if f == "ports":
> >                  continue
> >              p = os.path.join(path, f)
> > -            if os.path.isfile(p):
> > +            if os.path.isfile(p) and os.access(p, os.R_OK):  
> 
> Have you tested this? Looks like python always returns True here when
> run as root, and this script requires root (and checks for it).

Yeah, you definitely haven't tested this. Even if it worked we'd fall
into the else condition and say:

Exception: /sys/kernel/debug/netdevsim/netdevsim0//ports/0/dev/take_snapshot is neither file nor directory

> Also the fix is needed in net, not sure why you sent it to net-next.
> 
> >                  _, out = cmd('cat %s/%s' % (path, f))
> >                  dfs[f] = out.strip()
> >              elif os.path.isdir(p):