Eric W. Biederman [ebiederm@xxxxxxxxxxxx] wrote: | > | + if (target < RESERVED_PIDS) | > | > Should we replace RESERVED_PIDS with 0 ? We currently allow new | > containers to have pids 1..32K in the first pass and in subsequent | > passes assign starting at RESERVED_PIDS. | | If it is a preexisting namespace pid namespace removing the RESERVED_PIDS | check removes most if not all of the point of RESERVED_PIDS. | | In a new fresh pid namespace I have no problem with not performing | the RESERVED_PIDS check. In that case can we do this if (target_pid < RESERVED_PIDS && !pid_ns->level) return -EINVAL; instead ? | | So I guess that makes the check. | | if ((target < RESERVED_PIDS) && pid_ns->last_pid >= RESERVED_PIDS) | return -EINVAL; I am just wondering if there is a small corner case where C/R would randomly fail because of this sequence: - C/R code calls clone() or clone3() say about RESERVED_PIDS-1 times and ->last_pid == RESERVED_PIDS-1. - C/R code calls normal fork()/alloc_pidmap() for a short-lived child - its pid == ->last_pid == RESERVED_PIDS - C/R code then calls clone3()/set_pidmap() to set the pid of a new child to RESERVED_PID but fails (i.e it fails to restore a pid even when the pid is not in use). We could argue that mixing alloc_pidmap() and set_pidmap() during restart is bad since set_pidmap() may fail. The C/R developer could argue that we are forcing them to specify a pid even for a short lived process that they wait()s on and thus ensure that pid is not in use. Anyway, is RESERVED_PIDS meant for initial kernel-threads/daemons - if so would it be ok enforce it only in init_pid_ns ? Sukadev _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
