On 3/8/20 10:38 PM, Eric W. Biederman wrote: > > The cred_guard_mutex is problematic. The cred_guard_mutex is held > over the userspace accesses as the arguments from userspace are read. > The cred_guard_mutex is held of PTRACE_EVENT_EXIT as the the other ... is held while waiting for the trace parent to handle PTRACE_EVENT_EXIT or something? I wonder if we also should mention that it is held while waiting for the trace parent to receive the exit code with "wait"? > threads are killed. The cred_guard_mutex is held over > "put_user(0, tsk->clear_child_tid)" in exit_mm(). > > Any of those can result in deadlock, as the cred_guard_mutex is held > over a possible indefinite userspace waits for userspace. > > Add exec_update_mutex that is only held over exec updating process Add ? > with the new contents of exec, so that code that needs not to be > confused by exec changing the mm and the cred in ways that can not > happen during ordinary execution of a process. > > The plan is to switch the users of cred_guard_mutex to > exec_udpate_mutex one by one. This lets us move forward while still s/udpate/update/ Bernd.
