On Thu, 28 Nov 2024 at 02:50, Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
>
> On Wed, 2024-11-27 at 13:20 -0800, Kumar Kartikeya Dwivedi wrote:
> > Ensure that when CAP_PERFMON is dropped, and the verifier sees
> > allow_ptr_leaks as false, we are not permitted to read from a
> > STACK_INVALID slot. Without the fix, the test will report unexpected
> > success in loading.
> >
> > Since we need to control the capabilities when loading this test to only
> > retain CAP_BPF, refactor support added to do the same for
> > test_verifier_mtu and reuse it for this selftest to avoid copy-paste.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> > ---
> > .../selftests/bpf/prog_tests/verifier.c | 41 ++++++++++++++++---
> > .../bpf/progs/verifier_stack_noperfmon.c | 21 ++++++++++
> > 2 files changed, 56 insertions(+), 6 deletions(-)
> > create mode 100644 tools/testing/selftests/bpf/progs/verifier_stack_noperfmon.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
> > index d9f65adb456b..aaf4324e8ef0 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/verifier.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
> > @@ -63,6 +63,7 @@
> > #include "verifier_prevent_map_lookup.skel.h"
> > #include "verifier_private_stack.skel.h"
> > #include "verifier_raw_stack.skel.h"
> > +#include "verifier_stack_noperfmon.skel.h"
> > #include "verifier_raw_tp_writable.skel.h"
> > #include "verifier_reg_equal.skel.h"
> > #include "verifier_ref_tracking.skel.h"
> > @@ -226,22 +227,50 @@ void test_verifier_xdp_direct_packet_access(void) { RUN(verifier_xdp_direct_pack
> > void test_verifier_bits_iter(void) { RUN(verifier_bits_iter); }
> > void test_verifier_lsm(void) { RUN(verifier_lsm); }
> >
> > -void test_verifier_mtu(void)
> > +static int test_verifier_disable_caps(__u64 *caps)
>
> The original thread [0] discusses __caps_unpriv macro.
> I'd prefer such macro over these changes to prog_tests/verifier.c,
> were there any technical problems with code suggested in [0]?
>
> [0] https://lore.kernel.org/bpf/a1e48f5d9ae133e19adc6adf27e19d585e06bab4.camel@xxxxxxxxx/#t
>
I think that patch worked as well, but I got to look at this now after
all these months, and concluded that
what Daniel did in
https://lore.kernel.org/bpf/20241021152809.33343-5-daniel@xxxxxxxxxxxxx
was also
acceptable and preferred.
I can add your patch to this set and respin, or post a follow-up converting
test_verifier_mtu to it as well. Whatever is preferred.
> > {
> > - __u64 caps = 0;
> > int ret;
> >
> > /* In case CAP_BPF and CAP_PERFMON is not set */
> > - ret = cap_enable_effective(1ULL << CAP_BPF | 1ULL << CAP_NET_ADMIN, &caps);
> > + ret = cap_enable_effective(1ULL << CAP_BPF | 1ULL << CAP_NET_ADMIN, caps);
> > if (!ASSERT_OK(ret, "set_cap_bpf_cap_net_admin"))
> > - return;
> > + return -EINVAL;
> > ret = cap_disable_effective(1ULL << CAP_SYS_ADMIN | 1ULL << CAP_PERFMON, NULL);
> > if (!ASSERT_OK(ret, "disable_cap_sys_admin"))
> > + return -EINVAL;
> > + return 0;
> > +}
>
> [...]
>
