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Message-ID: <20241030052933.1041408-1-yun.zhou@windriver.com>
Date: Wed, 30 Oct 2024 13:29:33 +0800
From: Yun Zhou <yun.zhou@...driver.com>
To: <mcgrof@...nel.org>, <kees@...nel.org>, <joel.granados@...nel.org>,
<rostedt@...dmis.org>, <mhiramat@...nel.org>,
<mathieu.desnoyers@...icios.com>, <yun.zhou@...driver.com>
CC: <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
<linux-trace-kernel@...r.kernel.org>
Subject: [PATCH] kernel: add pid_max to pid_namespace
It is necessary to have a different pid_max in different containers.
For example, multiple containers are running on a host, one of which
is Android, and its 32 bit bionic libc only accepts pid <= 65535. So
it requires the global pid_max <= 65535. This will cause configuration
conflicts with other containers and also limit the maximum number of
tasks for the entire system.
Signed-off-by: Yun Zhou <yun.zhou@...driver.com>
---
include/linux/pid_namespace.h | 1 +
kernel/pid.c | 12 +++++------
kernel/pid_namespace.c | 35 ++++++++++++++++++++++++++-----
kernel/sysctl.c | 9 --------
kernel/trace/pid_list.c | 2 +-
kernel/trace/trace.h | 2 --
kernel/trace/trace_sched_switch.c | 2 +-
7 files changed, 39 insertions(+), 24 deletions(-)
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index f9f9931e02d6..064cfe2542fc 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -38,6 +38,7 @@ struct pid_namespace {
struct ucounts *ucounts;
int reboot; /* group exit code if this pidns was rebooted */
struct ns_common ns;
+ int pid_max;
#if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
int memfd_noexec_scope;
#endif
diff --git a/kernel/pid.c b/kernel/pid.c
index 2715afb77eab..f8026a61436b 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -60,8 +60,6 @@ struct pid init_struct_pid = {
}, }
};
-int pid_max = PID_MAX_DEFAULT;
-
int pid_max_min = RESERVED_PIDS + 1;
int pid_max_max = PID_MAX_LIMIT;
/*
@@ -78,6 +76,7 @@ static u64 pidfs_ino = RESERVED_PIDS;
*/
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,
@@ -198,7 +197,7 @@ 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
@@ -238,7 +237,7 @@ 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();
@@ -653,11 +652,12 @@ 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 d70ab49d5b4a..d8ddc0c56599 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -111,6 +111,7 @@ 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
@@ -280,19 +281,45 @@ static int pid_ns_ctl_handler(const struct ctl_table *table, int write,
return ret;
}
+#endif /* CONFIG_CHECKPOINT_RESTORE */
+
+static int pid_max_ns_ctl_handler(const struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct pid_namespace *pid_ns = task_active_pid_ns(current);
+ struct ctl_table tmp = *table;
+
+ if (write && !checkpoint_restore_ns_capable(pid_ns->user_ns))
+ return -EPERM;
+
+ tmp.data = &pid_ns->pid_max;
+ if (pid_ns->parent)
+ tmp.extra2 = &pid_ns->parent->pid_max;
+
+ return proc_dointvec_minmax(&tmp, 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,
+ },
+ { }
+};
int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
{
@@ -449,9 +476,7 @@ 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 79e6cb1d5c48..676a0d675e7f 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1804,15 +1804,6 @@ 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 4966e6bbdf6f..c62b9b3cfb3d 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.h b/kernel/trace/trace.h
index c866991b9c78..e51851d64e4d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -715,8 +715,6 @@ 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,
diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index 8a407adb0e1c..c20c80abe065 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -442,7 +442,7 @@ int trace_alloc_tgid_map(void)
if (tgid_map)
return 0;
- tgid_map_max = pid_max;
+ tgid_map_max = init_pid_ns.pid_max;
map = kvcalloc(tgid_map_max + 1, sizeof(*tgid_map),
GFP_KERNEL);
if (!map)
--
2.27.0
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