[PATCH v3 0/4] arm64, riscv: release shadow stacks on failed fork

["Iván Ezequiel Rodriguez" <ivanrwcm25@gmail.com>]

clone3(CLONE_VM|CLONE_PIDFD) can fail in put_user() after copy_thread()
has mapped a shadow stack into the shared mm. copy_process() then calls
exit_thread(). arm64 and riscv did not implement it, so the VMA leaked.

x86 already frees via exit_thread() -> shstk_free(). Its separate TLS
leak is when copy_thread() fails after the alloc and skips exit_thread().

Changes since v2:
- Move gcs_reset_thread() into process.c (Mark Brown).
- Spell out the x86 vs arm64/riscv difference above.

v2: https://lore.kernel.org/all/cover.1792519121.git.ivanrwcm25@gmail.com/

Assisted-by: LLM


Iván Ezequiel Rodriguez (4):
  arm64/gcs: release GCS on failed fork
  riscv/shstk: release shadow stack on failed fork
  selftests/arm64: GCS must not leak on a failed clone3
  selftests/riscv: shadow stack must not leak on a failed clone3

 arch/arm64/Kconfig                            |   1 +
 arch/arm64/kernel/process.c                   |  16 ++
 arch/riscv/Kconfig                            |   1 +
 arch/riscv/kernel/process.c                   |   9 +
 tools/testing/selftests/arm64/gcs/Makefile    |   3 +-
 .../selftests/arm64/gcs/gcs-clone-pidfd.c     | 168 +++++++++++++++++
 .../testing/selftests/arm64/gcs/gcs-locking.c |  20 --
 tools/testing/selftests/arm64/gcs/gcs-util.h  |  24 +++
 tools/testing/selftests/arm64/gcs/libc-gcs.c  |  20 --
 tools/testing/selftests/riscv/cfi/Makefile    |   5 +-
 .../selftests/riscv/cfi/shstk-clone-pidfd.c   | 173 ++++++++++++++++++
 11 files changed, 398 insertions(+), 42 deletions(-)
 create mode 100644 tools/testing/selftests/arm64/gcs/gcs-clone-pidfd.c
 create mode 100644 tools/testing/selftests/riscv/cfi/shstk-clone-pidfd.c

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2.43.0