Bernd, everyone
This is how I think the infrastructure change should look that makes way for fixing this issue.
- Cleanup and reorder the code so code that can potentially wait indefinitely for userspace comes at the beginning for flush_old_exec. - Add a new mutex and take it after we have passed any potential indefinite waits for userspace.
Then I think it is just going through the existing users of cred_guard_mutex and fixing them to use the new one.
There really aren't that many users of cred_guard_mutex so we should be able to get through the easy ones fairly quickly. And anything that isn't easy we can wait until we have a good fix.
The users of cred_guard_mutex that I saw were: fs/proc/base.c: proc_pid_attr_write do_io_accounting proc_pid_stack proc_pid_syscall proc_pid_personality
perf_event_open mm_access kcmp pidfd_fget seccomp_set_mode_filter
Bernd I think I have addressed the issues you pointed out in v1. Please let me know if you see anything else.
Eric W. Biederman (5): exec: Only compute current once in flush_old_exec exec: Factor unshare_sighand out of de_thread and call it separately exec: Move cleanup of posix timers on exec out of de_thread exec: Move exec_mmap right after de_thread in flush_old_exec exec: Add a exec_update_mutex to replace cred_guard_mutex
fs/exec.c | 65 ++++++++++++++++++++++++++++++-------------- include/linux/sched/signal.h | 9 +++++- init/init_task.c | 1 + kernel/fork.c | 1 + 4 files changed, 54 insertions(+), 22 deletions(-)