From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753697Ab2KLQK5 (ORCPT ); Mon, 12 Nov 2012 11:10:57 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:34433 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753620Ab2KLQK4 (ORCPT ); Mon, 12 Nov 2012 11:10:56 -0500 From: David Herrmann To: fuse-devel@lists.sourceforge.net Cc: Miklos Szeredi , Tejun Heo , linux-kernel@vger.kernel.org, David Herrmann Subject: [PATCH] cuse: do not register multiple devices with the same name Date: Mon, 12 Nov 2012 17:15:48 +0100 Message-Id: <1352736948-18243-1-git-send-email-dh.herrmann@googlemail.com> X-Mailer: git-send-email 1.8.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We do not check whether we already registered a CUSE device with a given name so we might end up with two devices with the same name. Sysfs will then complain as it cannot create suitable directories. This patch makes the init-command fail if there is already a device with the given name. To avoid race-conditions during initialization, we actually need to add the device to the list while still holding the lock for the name-check. The new "ready" field guarantees that the device is still not opened until it is fully initialized. Following the sysfs warnings when registering two devices with the same name: ------------[ cut here ]------------ WARNING: at fs/sysfs/dir.c:529 sysfs_add_one+0xc8/0xf0() Hardware name: N150P/N210P/N220P sysfs: cannot create duplicate filename '/devices/virtual/cuse/ttyFseat0' Modules linked in: btusb bluetooth Pid: 14089, comm: lt-kmscon Tainted: G W 3.5.3+ #60 Call Trace: [] ? sysfs_add_one+0x60/0xf0 [] warn_slowpath_common+0x7d/0xc0 [] warn_slowpath_fmt+0x43/0x50 [] sysfs_add_one+0xc8/0xf0 [] create_dir+0x76/0xd0 [] sysfs_create_dir+0x84/0xe0 [] kobject_add_internal+0x9b/0x200 [] kobject_add+0x68/0xc0 [] device_add+0xe3/0x680 [] ? dev_set_name+0x3e/0x40 [] cuse_process_init_reply+0x204/0x410 [] ? cuse_open+0xe0/0xe0 [] request_end+0xfc/0x1a0 [] fuse_dev_do_write+0xa32/0xd10 [] ? fuse_copy_one+0x45/0x60 [] ? find_get_page+0x66/0xb0 [] ? fuse_dev_splice_write+0x300/0x300 [] fuse_dev_write+0x69/0x80 [] do_sync_readv_writev+0xdc/0x120 [] ? rw_copy_check_uvector+0x6b/0x130 [] ? handle_mm_fault+0x12e/0x1f0 [] do_readv_writev+0xd3/0x1e0 [] vfs_writev+0x30/0x60 [] sys_writev+0x48/0xb0 [] system_call_fastpath+0x16/0x1b ---[ end trace 368eb04507b14c94 ]--- Signed-off-by: David Herrmann --- Hi I am not sure whether this qualifies for the stable-tree, so please CC stable@vger.kernel.org if you think so. The patch is against linux-next from today. Regards David fs/fuse/cuse.c | 35 +++++++++++++++++++++++++++++------ 1 file changed, 29 insertions(+), 6 deletions(-) diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c index 1326051..11fbc52 100644 --- a/fs/fuse/cuse.c +++ b/fs/fuse/cuse.c @@ -33,6 +33,7 @@ * closed. */ +#include #include #include #include @@ -45,6 +46,7 @@ #include #include #include +#include #include #include #include @@ -54,6 +56,7 @@ #define CUSE_CONNTBL_LEN 64 struct cuse_conn { + atomic_t ready; /* device is ready for open() */ struct list_head list; /* linked on cuse_conntbl */ struct fuse_conn fc; /* fuse connection */ struct cdev *cdev; /* associated character device */ @@ -120,6 +123,10 @@ static int cuse_open(struct inode *inode, struct file *file) spin_lock(&cuse_lock); list_for_each_entry(pos, cuse_conntbl_head(devt), list) if (pos->dev->devt == devt) { + if (!atomic_read(&pos->ready)) + break; + smp_rmb(); + fuse_conn_get(&pos->fc); cc = pos; break; @@ -308,7 +315,7 @@ static void cuse_gendev_release(struct device *dev) */ static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req) { - struct cuse_conn *cc = fc_to_cc(fc); + struct cuse_conn *cc = fc_to_cc(fc), *pos; struct cuse_init_out *arg = req->out.args[0].value; struct page *page = req->pages[0]; struct cuse_devinfo devinfo = { }; @@ -357,17 +364,30 @@ static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req) dev->devt = devt; dev->release = cuse_gendev_release; dev_set_drvdata(dev, cc); + + /* make sure the device-name is unique */ + spin_lock(&cuse_lock); dev_set_name(dev, "%s", devinfo.name); + list_for_each_entry(pos, cuse_conntbl_head(devt), list) { + if (!strcmp(dev_name(pos->dev), dev_name(dev))) { + spin_unlock(&cuse_lock); + goto err_device; + } + } + + list_add(&cc->list, cuse_conntbl_head(devt)); + spin_unlock(&cuse_lock); + rc = device_add(dev); if (rc) - goto err_device; + goto err_list; /* register cdev */ rc = -ENOMEM; cdev = cdev_alloc(); if (!cdev) - goto err_device; + goto err_list; cdev->owner = THIS_MODULE; cdev->ops = &cuse_frontend_fops; @@ -380,9 +400,8 @@ static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req) cc->cdev = cdev; /* make the device available */ - spin_lock(&cuse_lock); - list_add(&cc->list, cuse_conntbl_head(devt)); - spin_unlock(&cuse_lock); + smp_wmb(); + atomic_inc(&cc->ready); /* announce device availability */ dev_set_uevent_suppress(dev, 0); @@ -394,6 +413,10 @@ out: err_cdev: cdev_del(cdev); +err_list: + spin_lock(&cuse_lock); + list_del_init(&cc->list); + spin_unlock(&cuse_lock); err_device: put_device(dev); err_region: -- 1.8.0