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References: <20220421132317.1583867-1-asavkov@redhat.com> <e5919342-0697-65f0-063f-4941e74fe1ca@iogearbox.net>
In-Reply-To: <e5919342-0697-65f0-063f-4941e74fe1ca@iogearbox.net>
From:   Andrii Nakryiko <andrii.nakryiko@gmail.com>
Date:   Thu, 21 Apr 2022 09:57:29 -0700
Message-ID: <CAEf4BzZPStrod9Yj7nrDmXeZ0g_ThnaxVum9nEAcwAwAj=8iNg@mail.gmail.com>
Subject: Re: [PATCH bpf-next] selftests/bpf: fix prog_tests/uprobe_autoattach
 compilation error
To:     Daniel Borkmann <daniel@iogearbox.net>
Cc:     Artem Savkov <asavkov@redhat.com>,
        Alan Maguire <alan.maguire@oracle.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>, bpf <bpf@vger.kernel.org>,
        Networking <netdev@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>
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On Thu, Apr 21, 2022 at 9:53 AM Daniel Borkmann <daniel@iogearbox.net> wrot=
e:
>
> On 4/21/22 3:23 PM, Artem Savkov wrote:
> > I am getting the following compilation error for prog_tests/uprobe_auto=
attach.c
> >
> > tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c: In function=
 =E2=80=98test_uprobe_autoattach=E2=80=99:
> > ./test_progs.h:209:26: error: pointer =E2=80=98mem=E2=80=99 may be used=
 after =E2=80=98free=E2=80=99 [-Werror=3Duse-after-free]
> >
> > mem variable is now used in one of the asserts so it shouldn't be freed=
 right
> > away. Move free(mem) after the assert block.
>
> Looks good, but I rephrased this a bit to avoid confusion. It's false pos=
itive given we
> only compare the addresses but don't deref mem, which the compiler might =
not be able to
> follow in this case.
>

Great, thanks Daniel!

> https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?=
id=3D6a12b8e20d7e72386594a9dbe7bf2d7fae3b3aa6
>
> Thanks,
> Daniel
>
> > Fixes: 1717e248014c ("selftests/bpf: Uprobe tests should verify param/r=
eturn values")
> > Signed-off-by: Artem Savkov <asavkov@redhat.com>
> > ---
> >   tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c=
 b/tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c
> > index d6003dc8cc99..35b87c7ba5be 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c
> > @@ -34,7 +34,6 @@ void test_uprobe_autoattach(void)
> >
> >       /* trigger & validate shared library u[ret]probes attached by nam=
e */
> >       mem =3D malloc(malloc_sz);
> > -     free(mem);
> >
> >       ASSERT_EQ(skel->bss->uprobe_byname_parm1, trigger_val, "check_upr=
obe_byname_parm1");
> >       ASSERT_EQ(skel->bss->uprobe_byname_ran, 1, "check_uprobe_byname_r=
an");
> > @@ -44,6 +43,8 @@ void test_uprobe_autoattach(void)
> >       ASSERT_EQ(skel->bss->uprobe_byname2_ran, 3, "check_uprobe_byname2=
_ran");
> >       ASSERT_EQ(skel->bss->uretprobe_byname2_rc, mem, "check_uretprobe_=
byname2_rc");
> >       ASSERT_EQ(skel->bss->uretprobe_byname2_ran, 4, "check_uretprobe_b=
yname2_ran");
> > +
> > +     free(mem);
> >   cleanup:
> >       test_uprobe_autoattach__destroy(skel);
> >   }
> >
>