Messages in this thread | | | Date | Tue, 29 Nov 2011 22:12:19 +0400 | From | Pavel Emelyanov <> | Subject | Re: [PATCH] sysctl: Add the kernel.ns_last_pid control |
| |
On 11/29/2011 09:47 PM, Oleg Nesterov wrote: > On 11/28, Pavel Emelyanov wrote: >> >> --- a/kernel/pid_namespace.c >> +++ b/kernel/pid_namespace.c >> @@ -191,9 +191,40 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns) >> return; >> } >> >> +static int pid_ns_ctl_handler(struct ctl_table *table, int write, >> + void __user *buffer, size_t *lenp, loff_t *ppos) >> +{ >> + struct ctl_table tmp = *table; >> + >> + if (write && !capable(CAP_SYS_ADMIN)) >> + return -EPERM; >> + >> + /* >> + * Writing directly to ns' last_pid field is OK, since this field >> + * is volatile in a living namespace anyway and a code writing to >> + * it should synchronize its usage with external means. >> + */ >> + >> + tmp.data = ¤t->nsproxy->pid_ns->last_pid; >> + return proc_dointvec(&tmp, write, buffer, lenp, ppos); >> +} >> + >> +static struct ctl_table pid_ns_ctl_table[] = { >> + { >> + .procname = "ns_last_pid", >> + .maxlen = sizeof(int), >> + .mode = 0666, /* permissions are checked in the handler */ >> + .proc_handler = pid_ns_ctl_handler, >> + }, >> + { } >> +}; >> + >> +static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } }; >> + >> static __init int pid_namespaces_init(void) >> { >> pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC); >> + register_sysctl_paths(kern_path, pid_ns_ctl_table); >> return 0; >> } > > Hmm. This way it depends on CONFIG_PID_NS.
Yes, since this _is_ for namespaces. As we've found out this is close to completely unusable in the initial namespace in which tasks are just forking without caring much about what CAP_SYS_ADMIN-s think about this.
> Can't we simply add an entry into kern_table[] ?
And store the .proc_handler function dealing with somewhat which is pid namespace specific in the same generic file?
> And without ns_, just /proc/sys/kernel/last_pid.
But that's the namespace's last pid, not just some system-wide last pid.
> Oleg. > > . >
| |