On Tue, Nov 17, 2020 at 1:43 AM Martin KaFai Lau <kafai@xxxxxx> wrote:
>
> On Mon, Nov 16, 2020 at 11:25:36PM +0000, KP Singh wrote:
> > From: KP Singh <kpsingh@xxxxxxxxxx>
> >
> > The test forks a child process, updates the local storage to set/unset
> > the securexec bit.
> >
> > The BPF program in the test attaches to bprm_creds_for_exec which checks
> > the local storage of the current task to set the secureexec bit on the
> > binary parameters (bprm).
> >
> > The child then execs a bash command with the environment variable
> > TMPDIR set in the envp. The bash command returns a different exit code
> > based on its observed value of the TMPDIR variable.
> >
> > Since TMPDIR is one of the variables that is ignored by the dynamic
> > loader when the secureexec bit is set, one should expect the
> > child execution to not see this value when the secureexec bit is set.
> >
> > Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx>
> > ---
> > .../selftests/bpf/prog_tests/test_bprm_opts.c | 124 ++++++++++++++++++
> > tools/testing/selftests/bpf/progs/bprm_opts.c | 34 +++++
> > 2 files changed, 158 insertions(+)
> > create mode 100644 tools/testing/selftests/bpf/prog_tests/test_bprm_opts.c
> > create mode 100644 tools/testing/selftests/bpf/progs/bprm_opts.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/test_bprm_opts.c b/tools/testing/selftests/bpf/prog_tests/test_bprm_opts.c
> > new file mode 100644
> > index 000000000000..cba1ef3dc8b4
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/test_bprm_opts.c
> > @@ -0,0 +1,124 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +/*
> > + * Copyright (C) 2020 Google LLC.
> > + */
> > +
> > +#include <asm-generic/errno-base.h>
> > +#include <sys/stat.h>
> Is it needed?
No, Good catch, removed.
>
> > +#include <test_progs.h>
[...]
> > + * If the value of TMPDIR is set, the bash command returns 10
> > + * and if the value is unset, it returns 20.
> > + */
> > + ret = execle("/bin/bash", "bash", "-c",
> > + "[[ -z \"${TMPDIR}\" ]] || exit 10 && exit 20",
> > + NULL, bash_envp);
> > + if (ret)
> It should never reach here? May be just exit() unconditionally
> instead of having a chance to fall-through and then return -EINVAL.
Agreed. changed it to exit(errno); here.
>
> > + exit(errno);
> > + } else if (child_pid > 0) {
> > + waitpid(child_pid, &child_status, 0);
> > + ret = WEXITSTATUS(child_status);
> > +
> > + /* If a secureexec occured, the exit status should be 20.
> > + */
> > + if (secureexec && ret == 20)
> > + return 0;
> > +
> > + /* If normal execution happened the exit code should be 10.
> > + */
> > + if (!secureexec && ret == 10)
> > + return 0;
> > +
> > + return ret;
> Any chance that ret may be 0?
I think it's safer to just let it fall through and return -EINVAL, so
I removed the return ret here.
>
> > + }
[...]
> > + 0 /* secureexec */);
> > + if (CHECK(err, "run_set_secureexec:0", "err = %d", err))
> nit. err = %d"\n"
Fixed.
>
> > + goto close_prog;
> > +
> > + /* Run the test with the secureexec bit set */
> > + err = run_set_secureexec(bpf_map__fd(skel->maps.secure_exec_task_map),
> > + 1 /* secureexec */);
> > + if (CHECK(err, "run_set_secureexec:1", "err = %d", err))
> Same here.
Fixed.
- KP
>
> Others LGTM.
