netdev - Re: [PATCH bpf-next V2 2/4] selftests/bpf: xdp_hw

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Message-ID: <73d3e5c5-a38b-6f83-3022-b0442203ad6b@redhat.com>
Date:   Wed, 1 Feb 2023 18:53:44 +0100
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Martin KaFai Lau <martin.lau@...ux.dev>,
        Stanislav Fomichev <sdf@...gle.com>
Cc:     brouer@...hat.com, netdev@...r.kernel.org, martin.lau@...nel.org,
        ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        song@...nel.org, yhs@...com, john.fastabend@...il.com,
        dsahern@...il.com, willemb@...gle.com, void@...ifault.com,
        kuba@...nel.org, xdp-hints@...-project.net, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next V2 2/4] selftests/bpf: xdp_hw_metadata cleanup
 cause segfault



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);
  }