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-rw-r--r--Documentation/sysctl/kernel.txt8
-rw-r--r--kernel/pid.c4
-rw-r--r--kernel/pid_namespace.c31
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 = &current->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;
}