From: Davidlohr Bueso <dave@stgolabs.net> stable inclusion from stable-v5.10.85 commit 5dfe61147442cb9eedeb282630abf304144bc71c bugzilla: 186032 https://gitee.com/openeuler/kernel/issues/I4QVI4 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit e6a59aac8a8713f335a37d762db0dbe80e7f6d38 upstream. do_each_pid_thread(PIDTYPE_PGID) can race with a concurrent change_pid(PIDTYPE_PGID) that can move the task from one hlist to another while iterating. Serialize ioprio_get to take the tasklist_lock in this case, just like it's set counterpart. Fixes: d69b78ba1de (ioprio: grab rcu_read_lock in sys_ioprio_{set,get}()) Acked-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Link: https://lore.kernel.org/r/20211210182058.43417-1-dave@stgolabs.net Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Chen Jun <chenjun102@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- block/ioprio.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block/ioprio.c b/block/ioprio.c index 84da6c71b2cc..c8878647de40 100644 --- a/block/ioprio.c +++ b/block/ioprio.c @@ -214,6 +214,7 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who) pgrp = task_pgrp(current); else pgrp = find_vpid(who); + read_lock(&tasklist_lock); do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { tmpio = get_task_ioprio(p); if (tmpio < 0) @@ -223,6 +224,8 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who) else ret = ioprio_best(ret, tmpio); } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); + read_unlock(&tasklist_lock); + break; case IOPRIO_WHO_USER: uid = make_kuid(current_user_ns(), who); -- 2.20.1