From: Alberto Ruiz Date: Wed, 8 Apr 2026 15:23:40 +0000 (+0200) Subject: fuse: fix device node leak in cuse_process_init_reply() X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9fa4f7a53406430ee9982f2f636a15b338185122;p=thirdparty%2Fkernel%2Flinux.git fuse: fix device node leak in cuse_process_init_reply() If device_add() succeeds during CUSE initialization but a subsequent step (cdev_alloc() or cdev_add()) fails, the error path calls put_device() without first calling device_del(). This leaks the devtmpfs entry created by device_add(), leaving a stale /dev/ node that persists until reboot. Since the cuse_conn is never linked into cuse_conntbl on the failure path, cuse_channel_release() sees cc->dev == NULL and skips device_unregister(), so no other code path cleans up the node. This has several consequences: - The device name is permanently poisoned: any subsequent attempt to create a CUSE device with the same name hits the stale sysfs entry, device_add() fails, and the new device is aborted. - The collision manifests as ENODEV returned to userspace with no dmesg diagnostic, making it very difficult to debug. - The failure is self-perpetuating: once a name is leaked, all future attempts with that name fail identically. Fix this by introducing an err_dev label that calls device_del() to undo device_add() before falling through to err_unlock. The existing err_unlock path from a device_add() failure correctly skips device_del() since the device was never added. Testing instructions can be found at the lore link below. Link: https://lore.kernel.org/all/20260408-wip-cuse-leak-fix-v1-0-1c028d575e97@redhat.com/ Signed-off-by: Alberto Ruiz Fixes: 151060ac1314 ("CUSE: implement CUSE - Character device in Userspace") Cc: stable@vger.kernel.org Signed-off-by: Miklos Szeredi --- diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c index 174333633471b..3d38828af41fc 100644 --- a/fs/fuse/cuse.c +++ b/fs/fuse/cuse.c @@ -391,7 +391,7 @@ static void cuse_process_init_reply(struct fuse_mount *fm, rc = -ENOMEM; cdev = cdev_alloc(); if (!cdev) - goto err_unlock; + goto err_dev; cdev->owner = THIS_MODULE; cdev->ops = &cuse_frontend_fops; @@ -417,6 +417,8 @@ out: err_cdev: cdev_del(cdev); +err_dev: + device_del(dev); err_unlock: mutex_unlock(&cuse_lock); put_device(dev);