[PATCH bpf-next 0/5] bpf: Add user memory access kfuncs for mm_struct

[Anastasios Papagiannis]

During exec, argument and environment strings are copied into the new
address space held by struct linux_binprm before that address space is
installed on the task_struct. Existing eBPF user memory helpers only
support reading from the old address space (i.e. current process)
and for this reason programs cannot access these strings from the
bprm_check_security LSM hook.

This series adds two sleepable BPF kfuncs for copying bytes or
NUL-terminated strings from the address space identified by a trusted
struct mm_struct pointer. To support the exec use case, it also marks
linux_binprm->mm as trusted-or-null. This allows BPF LSM programs to
read exec arguments before allowing the exec to continue.

The series also adds selftests covering both kfuncs and the
trusted-or-null annotation.

Anastasios Papagiannis (5):
  mm: Add copy_remote_mm_str()
  bpf: Add user memory access kfuncs for mm_struct
  bpf: Mark linux_binprm->mm as trusted-or-null
  selftests/bpf: Test trusted-or-null linux_binprm->mm
  selftests/bpf: Test mm_struct user memory kfuncs with linux_binprm

 include/linux/mm.h                            |  2 +
 kernel/bpf/helpers.c                          |  2 +
 kernel/bpf/verifier.c                         |  5 ++
 kernel/trace/bpf_trace.c                      | 83 +++++++++++++++++++
 mm/memory.c                                   | 25 +++++-
 mm/nommu.c                                    | 25 +++++-
 .../bpf/prog_tests/copy_from_user_bprm.c      | 52 ++++++++++++
 .../selftests/bpf/progs/copy_from_user_bprm.c | 77 +++++++++++++++++
 tools/testing/selftests/bpf/progs/lsm.c       |  5 +-
 .../selftests/bpf/progs/verifier_lsm.c        | 31 +++++++
 10 files changed, 304 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/copy_from_user_bprm.c
 create mode 100644 tools/testing/selftests/bpf/progs/copy_from_user_bprm.c


base-commit: d114bb98936770c501c958bf2bc5fb6b7c0bad7b
-- 
2.55.0