Commit 612dafab authored Feb 22, 2017 by Tetsuo Handa Committed by Linus Torvalds Feb 22, 2017

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
0c740d0a ("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>

parent 6302666d

block/ioprio.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -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);