[PATCH v3 net-next 00/12] bpf: rewrite value tracking in verifier

[Edward Cree]

This series simplifies alignment tracking, generalises bounds tracking and
 fixes some bounds-tracking bugs in the BPF verifier.  Pointer arithmetic on
 packet pointers, stack pointers, map value pointers and context pointers has
 been unified, and bounds on these pointers are only checked when the pointer
 is dereferenced.
Operations on pointers which destroy all relation to the original pointer
 (such as multiplies and shifts) are disallowed if !env->allow_ptr_leaks,
 otherwise they convert the pointer to an unknown scalar and feed it to the
 normal scalar arithmetic handling.
Pointer types have been unified with the corresponding adjusted-pointer types
 where those existed (e.g. PTR_TO_MAP_VALUE[_ADJ] or FRAME_PTR vs
 PTR_TO_STACK); similarly, CONST_IMM and UNKNOWN_VALUE have been unified into
 SCALAR_VALUE.
Pointer types (except CONST_PTR_TO_MAP, PTR_TO_MAP_VALUE_OR_NULL and
 PTR_TO_PACKET_END, which do not allow arithmetic) have a 'fixed offset' and
 a 'variable offset'; the former is used when e.g. adding an immediate or a
 known-constant register, as long as it does not overflow.  Otherwise the
 latter is used, and any operation creating a new variable offset creates a
 new 'id' (and, for PTR_TO_PACKET, clears the 'range').
SCALAR_VALUEs use the 'variable offset' fields to track the range of possible
 values; the 'fixed offset' should never be set on a scalar.

As of patch 12/12, all tests of tools/testing/selftests/bpf/test_verifier
 and tools/testing/selftests/bpf/test_align pass.

v3: added a few more tests; removed RFC tags.

v2: fixed nfp build, made test_align pass again and extended it with a few
 new tests (though still need to add more).

Edward Cree (12):
  selftests/bpf: add test for mixed signed and unsigned bounds checks
  bpf/verifier: rework value tracking
  nfp: change bpf verifier hooks to match new verifier data structures
  bpf/verifier: track signed and unsigned min/max values
  bpf/verifier: more concise register state logs for constant var_off
  selftests/bpf: change test_verifier expectations
  selftests/bpf: rewrite test_align
  selftests/bpf: add a test to test_align
  selftests/bpf: add test for bogus operations on pointers
  selftests/bpf: don't try to access past MAX_PACKET_OFF in
    test_verifier
  selftests/bpf: add tests for subtraction & negative numbers
  selftests/bpf: variable offset negative tests

 drivers/net/ethernet/netronome/nfp/bpf/verifier.c |   24 +-
 include/linux/bpf.h                               |   34 +-
 include/linux/bpf_verifier.h                      |   56 +-
 include/linux/tnum.h                              |   81 +
 kernel/bpf/Makefile                               |    2 +-
 kernel/bpf/tnum.c                                 |  180 ++
 kernel/bpf/verifier.c                             | 1943 ++++++++++++---------
 tools/testing/selftests/bpf/test_align.c          |  462 ++++-
 tools/testing/selftests/bpf/test_verifier.c       |  293 ++--
 9 files changed, 2034 insertions(+), 1041 deletions(-)
 create mode 100644 include/linux/tnum.h
 create mode 100644 kernel/bpf/tnum.c