Fix unsafe BPF_PROG_TEST_RUN interface

Right now, there is no safe way to use BPF_PROG_TEST_RUN with data_out. This is because bpf_test_finish copies the output buffer to user space without checking its size. This can lead to the kernel overwriting data in user space after the buffer if xdp_adjust_head and friends are in play.

Thanks to everyone for their advice and patience with this patch set!

Changes in v5:
* Fix up libbpf.map

Changes in v4:
* Document bpf_prog_test_run and bpf_prog_test_run_xattr
* Use struct bpf_prog_test_run_attr for return values

Changes in v3:
* Introduce bpf_prog_test_run_xattr instead of modifying the existing function

Changes in v2:
* Make the syscall return ENOSPC if data_size_out is too small
* Make bpf_prog_test_run return EINVAL if size_out is missing
* Document the new behaviour of data_size_out

Lorenz Bauer (4):
bpf: respect size hint to BPF_PROG_TEST_RUN if present
tools: sync uapi/linux/bpf.h
libbpf: add bpf_prog_test_run_xattr
selftests: add a test for bpf_prog_test_run_xattr

 include/uapi/linux/bpf.h                 |  7 ++-
 net/bpf/test_run.c                       | 15 ++++++-
 tools/include/uapi/linux/bpf.h           |  7 ++-
 tools/lib/bpf/bpf.c                      | 23 ++++++++++
 tools/lib/bpf/bpf.h                      | 19 ++++++++
 tools/lib/bpf/libbpf.map                 |  1 +
 tools/testing/selftests/bpf/test_progs.c | 55 +++++++++++++++++++++++-
 7 files changed, 120 insertions(+), 7 deletions(-)

2.19.1