This patchset addresses a race condition we've dealt with recently with seccomp. Specifically programs interrupting syscalls while they're in progress. This was exacerbated by Golang's recent adoption of "async preemption", in which they try to interrupt any syscall that's been running for more than 10ms during GC. During certain syscalls, it's non-trivial to write them in a reetrant manner in userspace (mount).
This has a couple semantic changes, and relaxes a check on seccomp_data, and changes the semantics with ordering of how addfd and notification replies in the supervisor are handled. It also follows up on the original proposal from Tycho[2] to allow for adding an FD and returning that value atomically. Changes since v1[1]: * Fix some documentation * Add Rata's patches to allow for direct return from addfd [1]: https://lore.kernel.org/lkml/20210220090502.7202-1-sar...@sargun.me/ [2]: https://lore.kernel.org/lkml/202012011322.26DCBC64F2@keescook/ Rodrigo Campos (1): seccomp: Support atomic "addfd + send reply" Sargun Dhillon (4): seccomp: Refactor notification handler to prepare for new semantics seccomp: Add wait_killable semantic to seccomp user notifier selftests/seccomp: Add test for wait killable notifier selftests/seccomp: Add test for atomic addfd+send .../userspace-api/seccomp_filter.rst | 15 +- include/uapi/linux/seccomp.h | 4 + kernel/seccomp.c | 129 ++++++++++++++---- tools/testing/selftests/seccomp/seccomp_bpf.c | 102 ++++++++++++++ 4 files changed, 220 insertions(+), 30 deletions(-) -- 2.25.1
