linux-kernel - [PATCH 1/2] block: Use for_each_thread() in sys_ioprio_set()/sys_ioprio

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Date:   Thu,  2 Feb 2017 22:22:58 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Oleg Nesterov <oleg@...hat.com>
Subject: [PATCH 1/2] block: Use for_each_thread() in sys_ioprio_set()/sys_ioprio_get()

IOPRIO_WHO_USER case in sys_ioprio_set()/sys_ioprio_get() are using
while_each_thread(), which is unsafe under RCU lock according to
commit 0c740d0afc3bff0a ("introduce for_each_thread() to replace
the buggy while_each_thread()"). Use for_each_thread() which is
safe under RCU lock.

Link: http://lkml.kernel.org/r/201702011947.DBD56740.OMVHOLOtSJFFFQ@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@...hat.com>
---
 block/ioprio.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/block/ioprio.c b/block/ioprio.c
index 01b8116..3790669 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -122,14 +122,14 @@ int set_task_ioprio(struct task_struct *task, int ioprio)
 			if (!user)
 				break;
 
-			do_each_thread(g, p) {
+			for_each_process_thread(g, p) {
 				if (!uid_eq(task_uid(p), uid) ||
 				    !task_pid_vnr(p))
 					continue;
 				ret = set_task_ioprio(p, ioprio);
 				if (ret)
 					goto free_uid;
-			} while_each_thread(g, p);
+			}
 free_uid:
 			if (who)
 				free_uid(user);
@@ -222,7 +222,7 @@ int ioprio_best(unsigned short aprio, unsigned short bprio)
 			if (!user)
 				break;
 
-			do_each_thread(g, p) {
+			for_each_process_thread(g, p) {
 				if (!uid_eq(task_uid(p), user->uid) ||
 				    !task_pid_vnr(p))
 					continue;
@@ -233,7 +233,7 @@ int ioprio_best(unsigned short aprio, unsigned short bprio)
 					ret = tmpio;
 				else
 					ret = ioprio_best(ret, tmpio);
-			} while_each_thread(g, p);
+			}
 
 			if (who)
 				free_uid(user);
-- 
1.8.3.1