netdev - Re: [PATCH bpf-next] selftests/xsk: fix double free

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Message-ID: <CAJ8uoz2Z1amorsKx3Fm7Hy+mfK9+e-KYffT-N9CauYxkapQ29Q@mail.gmail.com>
Date:   Fri, 30 Sep 2022 09:52:32 +0200
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     Martin KaFai Lau <martin.lau@...ux.dev>
Cc:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        magnus.karlsson@...el.com, bjorn@...nel.org, ast@...nel.org,
        daniel@...earbox.net, netdev@...r.kernel.org,
        jonathan.lemon@...il.com, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next] selftests/xsk: fix double free

On Fri, Sep 30, 2022 at 2:52 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 9/29/22 3:44 AM, Maciej Fijalkowski wrote:
> > On Thu, Sep 29, 2022 at 11:01:33AM +0200, Magnus Karlsson wrote:
> >> From: Magnus Karlsson <magnus.karlsson@...el.com>
> >>
> >> Fix a double free at exit of the test suite.
> >>
> >> Fixes: a693ff3ed561 ("selftests/xsk: Add support for executing tests on physical device")
> >> Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
> >> ---
> >>   tools/testing/selftests/bpf/xskxceiver.c | 3 ---
> >>   1 file changed, 3 deletions(-)
> >>
> >> diff --git a/tools/testing/selftests/bpf/xskxceiver.c b/tools/testing/selftests/bpf/xskxceiver.c
> >> index ef33309bbe49..d1a5f3218c34 100644
> >> --- a/tools/testing/selftests/bpf/xskxceiver.c
> >> +++ b/tools/testing/selftests/bpf/xskxceiver.c
> >> @@ -1953,9 +1953,6 @@ int main(int argc, char **argv)
> >>
> >>      pkt_stream_delete(tx_pkt_stream_default);
> >>      pkt_stream_delete(rx_pkt_stream_default);
> >> -    free(ifobj_rx->umem);
> >> -    if (!ifobj_tx->shared_umem)
> shared_umem means ifobj_rx->umem and ifobj_tx->umem are the same?  No special
> handling is needed and ifobject_delete() will handle it?

You are correct, we will still have a double free in that case. Thanks
for spotting. Will send a v2.

> >> -            free(ifobj_tx->umem);
> >>      ifobject_delete(ifobj_tx);
> >>      ifobject_delete(ifobj_rx);
> >
> > So basically we free this inside ifobject_delete().
>