Hi, The goal of this patch series is to control script interpretation. A new O_MAYEXEC flag used by sys_open() is added to enable userland script interpreter to delegate to the kernel (and thus the system security policy) the permission to interpret scripts or other files containing what can be seen as commands. The security policy is the responsibility of an LSM. A basic system-wide policy is implemented with Yama and configurable through a sysctl. The initial idea come from CLIP OS and the original implementation has been used for more than 10 years: https://github.com/clipos-archive/clipos4_doc An introduction to O_MAYEXEC was given at the Linux Security Summit Europe 2018 - Linux Kernel Security Contributions by ANSSI: https://www.youtube.com/watch?v=chNjCRtPKQY&t=17m15s The "write xor execute" principle was explained at Kernel Recipes 2018 - CLIP OS: a defense-in-depth OS: https://www.youtube.com/watch?v=PjRE0uBtkHU&t=11m14s This patch series can be applied on top of v4.20-rc6. This can be tested with CONFIG_SECURITY_YAMA. I would really appreciate constructive comments on this RFC. Regards, Mickaël Salaün (5): fs: Add support for an O_MAYEXEC flag on sys_open() fs: Add a MAY_EXECMOUNT flag to infer the noexec mount propertie Yama: Enforces noexec mounts or file executability through O_MAYEXEC selftest/yama: Add tests for O_MAYEXEC enforcing doc: Add documentation for Yama's open_mayexec_enforce Documentation/admin-guide/LSM/Yama.rst | 41 +++ MAINTAINERS | 1 + fs/fcntl.c | 2 +- fs/namei.c | 2 + fs/open.c | 4 + include/linux/fcntl.h | 2 +- include/linux/fs.h | 4 + include/uapi/asm-generic/fcntl.h | 3 + security/yama/Kconfig | 3 +- security/yama/yama_lsm.c | 82 +++++- tools/testing/selftests/Makefile | 1 + tools/testing/selftests/yama/.gitignore | 1 + tools/testing/selftests/yama/Makefile | 19 ++ tools/testing/selftests/yama/config | 2 + tools/testing/selftests/yama/test_omayexec.c | 276 +++++++++++++++++++ 15 files changed, 439 insertions(+), 4 deletions(-) create mode 100644 tools/testing/selftests/yama/.gitignore create mode 100644 tools/testing/selftests/yama/Makefile create mode 100644 tools/testing/selftests/yama/config create mode 100644 tools/testing/selftests/yama/test_omayexec.c -- 2.20.0.rc2
