diff options
| -rw-r--r-- | Documentation/sysctl/kernel.txt | 8 | ||||
| -rw-r--r-- | kernel/pid.c | 4 | ||||
| -rw-r--r-- | kernel/pid_namespace.c | 31 |
3 files changed, 42 insertions, 1 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 6d8cd8b2c30d..8c20fbd8b42d 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -415,6 +415,14 @@ PIDs of value pid_max or larger are not allocated. ============================================================== +ns_last_pid: + +The last pid allocated in the current (the one task using this sysctl +lives in) pid namespace. When selecting a pid for a next task on fork +kernel tries to allocate a number starting from this one. + +============================================================== + powersave-nap: (PPC only) If set, Linux-PPC will use the 'nap' mode of powersaving, diff --git a/kernel/pid.c b/kernel/pid.c index fa5f72227e5f..ce8e00deaccb 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -137,7 +137,9 @@ static int pid_before(int base, int a, int b) } /* - * We might be racing with someone else trying to set pid_ns->last_pid. + * We might be racing with someone else trying to set pid_ns->last_pid + * at the pid allocation time (there's also a sysctl for this, but racing + * with this one is OK, see comment in kernel/pid_namespace.c about it). * We want the winner to have the "later" value, because if the * "earlier" value prevails, then a pid may get reused immediately. * diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index e9c9adc84ca6..a8968396046d 100644 --- 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; } |