[PATCH 0/6] objtool: UACCESS validation

[Peter Zijlstra]

Teach objtool to validate the UACCESS (SMAP, PAN) rules which are currently
unenforced and (therefore obviously) violated.

UACCESS sections should be small; we want to limit the amount of code that can
touch userspace. Furthermore, UACCESS state isn't scheduled, this means that
anything that directly calls into the scheduler will result in random code
running with UACCESS enabled and possibly getting back into the UACCESS region
with UACCESS disabled and causing faults.

Forbid any CALL/RET while UACCESS is enabled; but provide an annotation to mark
(a very limited) set of functions as UACCESS-safe (eg. the planned:
unsafe_copy_{to,from}_user()).

---
 arch/x86/ia32/ia32_signal.c     |  29 ++++---
 arch/x86/include/asm/uaccess.h  |   4 +-
 include/linux/frame.h           |  49 ++++++++++-
 tools/objtool/Makefile          |   2 +-
 tools/objtool/arch.h            |   6 +-
 tools/objtool/arch/x86/decode.c |  22 ++++-
 tools/objtool/check.c           | 180 ++++++++++++++++++++++++++++++----------
 tools/objtool/check.h           |   3 +-
 tools/objtool/elf.h             |   1 +
 9 files changed, 234 insertions(+), 62 deletions(-)