@@ -1043,6 +1043,8 @@ 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.
+When set to -1, first-fit pid numbering is used instead of the next-fit.
+
powersave-nap (PPC only)
========================
@@ -41,6 +41,9 @@ struct pid_namespace {
#if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
int memfd_noexec_scope;
#endif
+#ifdef CONFIG_IA32_EMULATION
+ bool pid_noncyclic;
+#endif
} __randomize_layout;
extern struct pid_namespace init_pid_ns;
@@ -191,6 +191,10 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
for (i = ns->level; i >= 0; i--) {
int tid = 0;
+ bool pid_noncyclic = 0;
+#ifdef CONFIG_IA32_EMULATION
+ pid_noncyclic = READ_ONCE(tmp->pid_noncyclic);
+#endif
if (set_tid_size) {
tid = set_tid[ns->level - i];
@@ -235,8 +239,12 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
* Store a null pointer so find_pid_ns does not find
* a partially initialized PID (see below).
*/
- nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
- pid_max, GFP_ATOMIC);
+ if (likely(!pid_noncyclic))
+ nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
+ pid_max, GFP_ATOMIC);
+ else
+ nr = idr_alloc(&tmp->idr, NULL, pid_min,
+ pid_max, GFP_ATOMIC);
}
spin_unlock_irq(&pidmap_lock);
idr_preload_end();
@@ -113,6 +113,9 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
ns->pid_allocated = PIDNS_ADDING;
#if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
ns->memfd_noexec_scope = pidns_memfd_noexec_scope(parent_pid_ns);
+#endif
+#ifdef CONFIG_IA32_EMULATION
+ ns->pid_noncyclic = READ_ONCE(parent_pid_ns->pid_noncyclic);
#endif
return ns;
@@ -260,7 +263,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
return;
}
-#ifdef CONFIG_CHECKPOINT_RESTORE
+#if defined(CONFIG_CHECKPOINT_RESTORE) || defined(CONFIG_IA32_EMULATION)
static int pid_ns_ctl_handler(const struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
@@ -271,12 +274,23 @@ static int pid_ns_ctl_handler(const struct ctl_table *table, int write,
if (write && !checkpoint_restore_ns_capable(pid_ns->user_ns))
return -EPERM;
- next = idr_get_cursor(&pid_ns->idr) - 1;
+ next = -1;
+#ifdef CONFIG_IA32_EMULATION
+ if (!pid_ns->pid_noncyclic)
+#endif
+ next += idr_get_cursor(&pid_ns->idr);
tmp.data = &next;
ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
- if (!ret && write)
- idr_set_cursor(&pid_ns->idr, next + 1);
+ if (!ret && write) {
+ if (next > -1)
+ idr_set_cursor(&pid_ns->idr, next + 1);
+ else if (!IS_ENABLED(CONFIG_IA32_EMULATION))
+ ret = -EINVAL;
+#ifdef CONFIG_IA32_EMULATION
+ WRITE_ONCE(pid_ns->pid_noncyclic, next == -1);
+#endif
+ }
return ret;
}
@@ -288,11 +302,11 @@ static const struct ctl_table pid_ns_ctl_table[] = {
.maxlen = sizeof(int),
.mode = 0666, /* permissions are checked in the handler */
.proc_handler = pid_ns_ctl_handler,
- .extra1 = SYSCTL_ZERO,
+ .extra1 = SYSCTL_NEG_ONE,
.extra2 = &pid_max,
},
};
-#endif /* CONFIG_CHECKPOINT_RESTORE */
+#endif /* CONFIG_CHECKPOINT_RESTORE || CONFIG_IA32_EMULATION */
int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
{
@@ -449,7 +463,7 @@ static __init int pid_namespaces_init(void)
{
pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC | SLAB_ACCOUNT);
-#ifdef CONFIG_CHECKPOINT_RESTORE
+#if defined(CONFIG_CHECKPOINT_RESTORE) || defined(CONFIG_IA32_EMULATION)
register_sysctl_init("kernel", pid_ns_ctl_table);
#endif
Noone would need to use this allocation strategy (it's slower, pid numbers collide sooner). Its primary purpose are pid namespaces in conjunction with pids.max cgroup limit which keeps (virtual) pid numbers below the given limit. This is for 32-bit userspace programs that may not work well with pid numbers above 65536. Link: https://lore.kernel.org/r/20241122132459.135120-1-aleksandr.mikhalitsyn@canonical.com/ Signed-off-by: Michal Koutný <mkoutny@suse.com> --- Documentation/admin-guide/sysctl/kernel.rst | 2 ++ include/linux/pid_namespace.h | 3 +++ kernel/pid.c | 12 +++++++-- kernel/pid_namespace.c | 28 +++++++++++++++------ 4 files changed, 36 insertions(+), 9 deletions(-)