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Message-ID: <20241004150521.361af760@gandalf.local.home>
Date: Fri, 4 Oct 2024 15:05:21 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Yun Zhou <yun.zhou@...driver.com>
Cc: <mcgrof@...nel.org>, <keescook@...omium.org>, <yzaikin@...gle.com>,
<mhiramat@...nel.org>, <mathieu.desnoyers@...icios.com>,
<linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
<linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH] kernel: add pid_max to pid_namespace
On Mon, 2 Sep 2024 19:49:20 +0800
Yun Zhou <yun.zhou@...driver.com> wrote:
-ENOCHANGELOG
What? Why? Why should I care about this?
A change log *must* have all the information to say why this change is
necessary. It's OK for the subject to state what it is doing, but there
most definitely needs a "why?" in the change log.
-- Steve
> Signed-off-by: Yun Zhou <yun.zhou@...driver.com>
> ---
> include/linux/pid_namespace.h | 1 +
> kernel/pid.c | 12 ++++++------
> kernel/pid_namespace.c | 33 ++++++++++++++++++++++++++++-----
> kernel/sysctl.c | 9 ---------
> kernel/trace/pid_list.c | 2 +-
> kernel/trace/trace.c | 2 +-
> kernel/trace/trace.h | 2 --
> 7 files changed, 37 insertions(+), 24 deletions(-)
>
> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
> index f9f9931e02d6..0e3c18f3cac5 100644
> --- a/include/linux/pid_namespace.h
> +++ b/include/linux/pid_namespace.h
> @@ -27,6 +27,7 @@ struct pid_namespace {
> struct idr idr;
> struct rcu_head rcu;
> unsigned int pid_allocated;
> + int pid_max;
> struct task_struct *child_reaper;
> struct kmem_cache *pid_cachep;
> unsigned int level;
> diff --git a/kernel/pid.c b/kernel/pid.c
> index 6500ef956f2f..14da3f68ceed 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -59,8 +59,6 @@ struct pid init_struct_pid = {
> }, }
> };
>
> -int pid_max = PID_MAX_DEFAULT;
> -
> #define RESERVED_PIDS 300
>
> int pid_max_min = RESERVED_PIDS + 1;
> @@ -74,6 +72,7 @@ int pid_max_max = PID_MAX_LIMIT;
> */
> struct pid_namespace init_pid_ns = {
> .ns.count = REFCOUNT_INIT(2),
> + .pid_max = PID_MAX_DEFAULT,
> .idr = IDR_INIT(init_pid_ns.idr),
> .pid_allocated = PIDNS_ADDING,
> .level = 0,
> @@ -194,7 +193,7 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
> tid = set_tid[ns->level - i];
>
> retval = -EINVAL;
> - if (tid < 1 || tid >= pid_max)
> + if (tid < 1 || tid >= tmp->pid_max)
> goto out_free;
> /*
> * Also fail if a PID != 1 is requested and
> @@ -234,7 +233,7 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
> * a partially initialized PID (see below).
> */
> nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
> - pid_max, GFP_ATOMIC);
> + tmp->pid_max, GFP_ATOMIC);
> }
> spin_unlock_irq(&pidmap_lock);
> idr_preload_end();
> @@ -651,11 +650,12 @@ void __init pid_idr_init(void)
> BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_ADDING);
>
> /* bump default and minimum pid_max based on number of cpus */
> - pid_max = min(pid_max_max, max_t(int, pid_max,
> + init_pid_ns.pid_max = min(pid_max_max, max_t(int, init_pid_ns.pid_max,
> PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
> pid_max_min = max_t(int, pid_max_min,
> PIDS_PER_CPU_MIN * num_possible_cpus());
> - pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min);
> + pr_info("pid_max: default: %u minimum: %u\n", init_pid_ns.pid_max,
> + pid_max_min);
>
> idr_init(&init_pid_ns.idr);
>
> diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
> index 3028b2218aa4..d6b3f34ecb25 100644
> --- a/kernel/pid_namespace.c
> +++ b/kernel/pid_namespace.c
> @@ -110,6 +110,7 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
> ns->user_ns = get_user_ns(user_ns);
> ns->ucounts = ucounts;
> ns->pid_allocated = PIDNS_ADDING;
> + ns->pid_max = parent_pid_ns->pid_max;
> #if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
> ns->memfd_noexec_scope = pidns_memfd_noexec_scope(parent_pid_ns);
> #endif
> @@ -295,20 +296,44 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write,
>
> return ret;
> }
> +#endif /* CONFIG_CHECKPOINT_RESTORE */
> +
> +static int pid_max_ns_ctl_handler(struct ctl_table *table, int write,
> + void *buffer, size_t *lenp, loff_t *ppos)
> +{
> + struct pid_namespace *pid_ns = task_active_pid_ns(current);
> +
> + if (write && !checkpoint_restore_ns_capable(pid_ns->user_ns))
> + return -EPERM;
> +
> + table->data = &pid_ns->pid_max;
> + if (pid_ns->parent)
> + table->extra2 = &pid_ns->parent->pid_max;
> +
> + return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
> +}
>
> -extern int pid_max;
> static struct ctl_table pid_ns_ctl_table[] = {
> +#ifdef CONFIG_CHECKPOINT_RESTORE
> {
> .procname = "ns_last_pid",
> .maxlen = sizeof(int),
> .mode = 0666, /* permissions are checked in the handler */
> .proc_handler = pid_ns_ctl_handler,
> .extra1 = SYSCTL_ZERO,
> - .extra2 = &pid_max,
> + .extra2 = &init_pid_ns.pid_max,
> + },
> +#endif /* CONFIG_CHECKPOINT_RESTORE */
> + {
> + .procname = "pid_max",
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = pid_max_ns_ctl_handler,
> + .extra1 = &pid_max_min,
> + .extra2 = &pid_max_max,
> },
> { }
> };
> -#endif /* CONFIG_CHECKPOINT_RESTORE */
>
> int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
> {
> @@ -465,9 +490,7 @@ static __init int pid_namespaces_init(void)
> {
> pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC | SLAB_ACCOUNT);
>
> -#ifdef CONFIG_CHECKPOINT_RESTORE
> register_sysctl_init("kernel", pid_ns_ctl_table);
> -#endif
>
> register_pid_ns_sysctl_table_vm();
> return 0;
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 157f7ce2942d..857bfdb39b15 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1809,15 +1809,6 @@ static struct ctl_table kern_table[] = {
> .proc_handler = proc_dointvec,
> },
> #endif
> - {
> - .procname = "pid_max",
> - .data = &pid_max,
> - .maxlen = sizeof (int),
> - .mode = 0644,
> - .proc_handler = proc_dointvec_minmax,
> - .extra1 = &pid_max_min,
> - .extra2 = &pid_max_max,
> - },
> {
> .procname = "panic_on_oops",
> .data = &panic_on_oops,
> diff --git a/kernel/trace/pid_list.c b/kernel/trace/pid_list.c
> index 95106d02b32d..ef52820e6719 100644
> --- a/kernel/trace/pid_list.c
> +++ b/kernel/trace/pid_list.c
> @@ -414,7 +414,7 @@ struct trace_pid_list *trace_pid_list_alloc(void)
> int i;
>
> /* According to linux/thread.h, pids can be no bigger that 30 bits */
> - WARN_ON_ONCE(pid_max > (1 << 30));
> + WARN_ON_ONCE(init_pid_ns.pid_max > (1 << 30));
>
> pid_list = kzalloc(sizeof(*pid_list), GFP_KERNEL);
> if (!pid_list)
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index fbcd3bafb93e..6295679ce16c 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -5415,7 +5415,7 @@ int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled)
>
> if (mask == TRACE_ITER_RECORD_TGID) {
> if (!tgid_map) {
> - tgid_map_max = pid_max;
> + tgid_map_max = init_pid_ns.pid_max;
> map = kvcalloc(tgid_map_max + 1, sizeof(*tgid_map),
> GFP_KERNEL);
>
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index b7f4ea25a194..df61b1db86a2 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -700,8 +700,6 @@ extern unsigned long tracing_thresh;
>
> /* PID filtering */
>
> -extern int pid_max;
> -
> bool trace_find_filtered_pid(struct trace_pid_list *filtered_pids,
> pid_t search_pid);
> bool trace_ignore_this_task(struct trace_pid_list *filtered_pids,
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