linux-kernel - [PATCH] x86/resctrl: Only show tasks' pids in current pid namespace

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Message-Id: <20230116071246.97717-1-shawnwang@linux.alibaba.com>
Date:   Mon, 16 Jan 2023 15:12:46 +0800
From:   Shawn Wang <shawnwang@...ux.alibaba.com>
To:     fenghua.yu@...el.com, reinette.chatre@...el.com
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, james.morse@....com, x86@...nel.org,
        hpa@...or.com, linux-kernel@...r.kernel.org
Subject: [PATCH] x86/resctrl: Only show tasks' pids in current pid namespace

When writing a task id to the "tasks" file in an rdtgroup,
rdtgroup_tasks_write() treats the pid as a number in the current pid
namespace. But when reading the "tasks" file, rdtgroup_tasks_show() shows
the list of global pids from the init namespace. If current pid namespace
is not the init namespace, pids in "tasks" will be confusing and incorrect.

To be more robust, let the "tasks" file only show pids in the current pid
namespace.

Signed-off-by: Shawn Wang <shawnwang@...ux.alibaba.com>
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 5993da21d822..9e97ae24c159 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -718,11 +718,15 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
 static void show_rdt_tasks(struct rdtgroup *r, struct seq_file *s)
 {
 	struct task_struct *p, *t;
+	pid_t pid;
 
 	rcu_read_lock();
 	for_each_process_thread(p, t) {
-		if (is_closid_match(t, r) || is_rmid_match(t, r))
-			seq_printf(s, "%d\n", t->pid);
+		if (is_closid_match(t, r) || is_rmid_match(t, r)) {
+			pid = task_pid_vnr(t);
+			if (pid)
+				seq_printf(s, "%d\n", pid);
+		}
 	}
 	rcu_read_unlock();
 }
-- 
2.27.0