Re: [PATCH bpf-next V2 2/4] selftests/bpf: xdp_hw_metadata cleanup cause segfault

[Jesper Dangaard Brouer <jbrouer@xxxxxxxxxx>]

On 01/02/2023 18.46, Martin KaFai Lau wrote:
> On 2/1/23 9:31 AM, Jesper Dangaard Brouer wrote:
> > diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c 
> > b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> > index 3823b1c499cc..438083e34cce 100644
> > --- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
> > +++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> > @@ -121,7 +121,7 @@ static void close_xsk(struct xsk *xsk)
> >           xsk_umem__delete(xsk->umem);
> >       if (xsk->socket)
> >           xsk_socket__delete(xsk->socket);
> > -    munmap(xsk->umem, UMEM_SIZE);
> > +    munmap(xsk->umem_area, UMEM_SIZE);
>
> Ah. Good catch. This should also explain a similar issue that CI is 
> seeing in the prog_tests/xdp_metadata.c.

Yes, very likely same bug in prog_tests/xdp_metadata.c.

It was super tricky (and time consuming) to find as I was debugging in
GDB and it didn't make sense that checking a value against NULL would
cause a segfault.  Plus, sometimes it worked without issues.

We also need this fix:

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c 
b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
index e033d48288c0..241909d71c7e 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
@@ -121,7 +121,7 @@ static void close_xsk(struct xsk *xsk)
                xsk_umem__delete(xsk->umem);
        if (xsk->socket)
                xsk_socket__delete(xsk->socket);
-       munmap(xsk->umem, UMEM_SIZE);
+       munmap(xsk->umem_area, UMEM_SIZE);
 }