linux-kernel - [PATCH] um: protect find_task_by_pid

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Message-ID: <TYCP286MB2323CA02DF3A741B5F58B297CA269@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM>
Date:   Sun, 16 Oct 2022 23:10:05 +0800
From:   Dawei Li <set_pte_at@...look.com>
To:     richard@....at, anton.ivanov@...bridgegreys.com,
        johannes@...solutions.net
Cc:     linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Dawei Li <set_pte_at@...look.com>
Subject: [PATCH] um: protect find_task_by_pid_ns() with rcu lock

find_task_by_pid_ns() is safe if and only if it's under protection
from rcu read lock, implements the protection.

base-commit: 193cb8372424184dde28088a4230a5fed0afb0ad

Signed-off-by: Dawei Li <set_pte_at@...look.com>
---
 arch/um/drivers/mconsole_kern.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
index 5026e7b9adfe..6b80e766ae80 100644
--- a/arch/um/drivers/mconsole_kern.c
+++ b/arch/um/drivers/mconsole_kern.c
@@ -683,7 +683,10 @@ void mconsole_stack(struct mc_request *req)
 		return;
 	}
 
+	rcu_read_lock();
 	to = find_task_by_pid_ns(pid_requested, &init_pid_ns);
+	rcu_read_unlock();
+
 	if ((to == NULL) || (pid_requested == 0)) {
 		mconsole_reply(req, "Couldn't find that pid", 1, 0);
 		return;
-- 
2.25.1