Prepare for moving elv_register[unregister]_queue out of elevator_lock & queue freezing, so we may have to call elv_unregister_queue() after elevator ->exit() is called, then there is small window for user to call into ->show()/store(), and user-after-free can be caused. Fail to show/store elevator sysfs attribute if elevator is dying by adding one new flag of ELEVATOR_FLAG_DYNG, which is protected by elevator ->sysfs_lock. Reviewed-by: Nilay Shroff <nilay@xxxxxxxxxxxxx> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- block/blk-mq-sched.c | 1 + block/elevator.c | 10 ++++++++-- block/elevator.h | 1 + 3 files changed, 10 insertions(+), 2 deletions(-) diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 336a15ffecfa..55a0fd105147 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -551,5 +551,6 @@ void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e) if (e->type->ops.exit_sched) e->type->ops.exit_sched(e); blk_mq_sched_tags_teardown(q, flags); + set_bit(ELEVATOR_FLAG_DYING, &q->elevator->flags); q->elevator = NULL; } diff --git a/block/elevator.c b/block/elevator.c index dde8732b7a26..48f2f202af98 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -426,7 +426,10 @@ elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) e = container_of(kobj, struct elevator_queue, kobj); mutex_lock(&e->sysfs_lock); - error = e->type ? entry->show(e, page) : -ENOENT; + if (test_bit(ELEVATOR_FLAG_DYING, &e->flags)) + error = -ENODEV; + else + error = e->type ? entry->show(e, page) : -ENOENT; mutex_unlock(&e->sysfs_lock); return error; } @@ -444,7 +447,10 @@ elv_attr_store(struct kobject *kobj, struct attribute *attr, e = container_of(kobj, struct elevator_queue, kobj); mutex_lock(&e->sysfs_lock); - error = e->type ? entry->store(e, page, length) : -ENOENT; + if (test_bit(ELEVATOR_FLAG_DYING, &e->flags)) + error = -ENODEV; + else + error = e->type ? entry->store(e, page, length) : -ENOENT; mutex_unlock(&e->sysfs_lock); return error; } diff --git a/block/elevator.h b/block/elevator.h index 9198676644a9..76a90a1b7ed6 100644 --- a/block/elevator.h +++ b/block/elevator.h @@ -121,6 +121,7 @@ struct elevator_queue }; #define ELEVATOR_FLAG_REGISTERED 0 +#define ELEVATOR_FLAG_DYING 1 /* * block elevator interface -- 2.47.0
