From: Hou Tao <houtao1@huawei.com> hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IB5UKT -------------------------------- When queuing ondemand_object_worker() to re-open the object, cachefiles_object is not pinned. The cachefiles_object may be freed when the pending read request is completed intentionally and the related erofs is umounted. If ondemand_object_worker() runs after the object is freed, it will incur use-after-free problem as shown below. process A processs B process C process D cachefiles_ondemand_send_req() // send a read req X // wait for its completion // close ondemand fd cachefiles_ondemand_fd_release() // set object as CLOSE cachefiles_ondemand_daemon_read() // set object as REOPENING queue_work(fscache_wq, &info->ondemand_work) // close /dev/cachefiles cachefiles_daemon_release cachefiles_flush_reqs complete(&req->done) // read req X is completed // umount the erofs fs cachefiles_put_object() // object will be freed cachefiles_ondemand_deinit_obj_info() kmem_cache_free(object) // both info and object are freed ondemand_object_worker() When dropping an object, it is no longer necessary to reopen the object, so use cancel_work_sync() to cancel or wait for ondemand_object_worker() to complete. Signed-off-by: Hou Tao <houtao1@huawei.com> Signed-off-by: Baokun Li <libaokun1@huawei.com> --- fs/cachefiles/ondemand.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c index e7caafd939c3..6d36d3e950e8 100644 --- a/fs/cachefiles/ondemand.c +++ b/fs/cachefiles/ondemand.c @@ -624,6 +624,9 @@ void cachefiles_ondemand_clean_object(struct cachefiles_object *object) } } xa_unlock(&cache->reqs); + + /* Wait for ondemand_object_worker() to finish. */ + cancel_work_sync(&object->private->work); } int cachefiles_ondemand_read(struct cachefiles_object *object, -- 2.46.1