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() (via
for_each_process_thread()) which is safe under RCU lock.

Link: http://lkml.kernel.org/r/201702011947.DBD56740.OMVHOLOtSJFFFQ@I-love.SAKURA.ne.jp
Link: http://lkml.kernel.org/r/1486041779-4401-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/block/ioprio.c b/block/ioprio.c
index 01b8116298a13b5463e7969ce66c0b037bcfccd5..3790669232ff5066175a2033ebd418a7c5a83f53 100644 (file)
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -122,14 +122,14 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, 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 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
                        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 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
                                        ret = tmpio;
                                else
                                        ret = ioprio_best(ret, tmpio);
-                       } while_each_thread(g, p);
+                       }
 
                        if (who)
                                free_uid(user);