This series was split off from the openat2(2) syscall discussion[1]. However, the copy_struct_to_user() helper has been dropped, because after some discussion it appears that there is no really obvious semantics for how copy_struct_to_user() should work on mixed-vintages (for instance, whether [2] is the correct semantics for all syscalls).
A common pattern for syscall extensions is increasing the size of a struct passed from userspace, such that the zero-value of the new fields result in the old kernel behaviour (allowing for a mix of userspace and kernel vintages to operate on one another in most cases). Previously there was no common lib/ function that implemented the necessary extension-checking semantics (and different syscalls implemented them slightly differently or incompletely[3]). This series implements the helper and ports several syscalls to use it. [1]: https://lore.kernel.org/lkml/20190904201933.10736-1-cyp...@cyphar.com/ [2]: commit 1251201c0d34 ("sched/core: Fix uclamp ABI bug, clean up and robustify sched_read_attr() ABI logic and code") [3]: For instance {sched_setattr,perf_event_open,clone3}(2) all do do similar checks to copy_struct_from_user() while rt_sigprocmask(2) always rejects differently-sized struct arguments. Aleksa Sarai (4): lib: introduce copy_struct_from_user() helper clone3: switch to copy_struct_from_user() sched_setattr: switch to copy_struct_from_user() perf_event_open: switch to copy_struct_from_user() include/linux/uaccess.h | 4 +++ include/uapi/linux/sched.h | 2 ++ kernel/events/core.c | 47 +++++------------------- kernel/fork.c | 34 ++++-------------- kernel/sched/core.c | 43 ++++------------------ lib/Makefile | 2 +- lib/strnlen_user.c | 52 +++++++++++++++++++++++++++ lib/struct_user.c | 73 ++++++++++++++++++++++++++++++++++++++ 8 files changed, 155 insertions(+), 102 deletions(-) create mode 100644 lib/struct_user.c -- 2.23.0
