From patchwork Thu Aug 13 15:32:03 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yishai Hadas X-Patchwork-Id: 7009071 Return-Path: X-Original-To: patchwork-linux-rdma@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 368EFC05AC for ; Thu, 13 Aug 2015 15:34:49 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id E6DAD20690 for ; Thu, 13 Aug 2015 15:34:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7CCE620608 for ; Thu, 13 Aug 2015 15:34:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752884AbbHMPei (ORCPT ); Thu, 13 Aug 2015 11:34:38 -0400 Received: from [193.47.165.129] ([193.47.165.129]:54007 "EHLO mellanox.co.il" rhost-flags-FAIL-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752866AbbHMPec (ORCPT ); Thu, 13 Aug 2015 11:34:32 -0400 Received: from Internal Mail-Server by MTLPINE1 (envelope-from yishaih@mellanox.com) with ESMTPS (AES256-SHA encrypted); 13 Aug 2015 18:34:05 +0300 Received: from vnc17.mtl.labs.mlnx (vnc17.mtl.labs.mlnx [10.7.2.17]) by labmailer.mlnx (8.13.8/8.13.8) with ESMTP id t7DFY453004012; Thu, 13 Aug 2015 18:34:04 +0300 Received: from vnc17.mtl.labs.mlnx (localhost.localdomain [127.0.0.1]) by vnc17.mtl.labs.mlnx (8.13.8/8.13.8) with ESMTP id t7DFY4n6009852; Thu, 13 Aug 2015 18:34:04 +0300 Received: (from yishaih@localhost) by vnc17.mtl.labs.mlnx (8.13.8/8.13.8/Submit) id t7DFY4x0009851; Thu, 13 Aug 2015 18:34:04 +0300 From: Yishai Hadas To: dledford@redhat.com Cc: linux-rdma@vger.kernel.org, yishaih@mellanox.com, raindel@mellanox.com, jackm@mellanox.com, haggaie@mellanox.com, jgunthorpe@obsidianresearch.com Subject: [PATCH for-next V8 2/6] IB/uverbs: Fix race between ib_uverbs_open and remove_one Date: Thu, 13 Aug 2015 18:32:03 +0300 Message-Id: <1439479927-8751-3-git-send-email-yishaih@mellanox.com> X-Mailer: git-send-email 1.7.11.3 In-Reply-To: <1439479927-8751-1-git-send-email-yishaih@mellanox.com> References: <1439479927-8751-1-git-send-email-yishaih@mellanox.com> Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Fixes: 2a72f212263701b927559f6850446421d5906c41 ("IB/uverbs: Remove dev_table") Before this commit there was a device look-up table that was protected by a spin_lock used by ib_uverbs_open and by ib_uverbs_remove_one. When it was dropped and container_of was used instead, it enabled the race with remove_one as dev might be freed just after: dev = container_of(inode->i_cdev, struct ib_uverbs_device, cdev) but before the kref_get. In addition, this buggy patch added some dead code as container_of(x,y,z) can never be NULL and so dev can never be NULL. As a result the comment above ib_uverbs_open saying "the open method will either immediately run -ENXIO" is wrong as it can never happen. The solution follows Jason Gunthorpe suggestion from below URL: https://www.mail-archive.com/linux-rdma@vger.kernel.org/msg25692.html cdev will hold a kref on the parent (the containing structure, ib_uverbs_device) and only when that kref is released it is guaranteed that open will never be called again. In addition, fixes the active count scheme to use an atomic not a kref to prevent WARN_ON as pointed by above comment from Jason. Signed-off-by: Yishai Hadas Signed-off-by: Shachar Raindel Reviewed-by: Jason Gunthorpe --- drivers/infiniband/core/uverbs.h | 3 +- drivers/infiniband/core/uverbs_main.c | 43 +++++++++++++++++++++++---------- 2 files changed, 32 insertions(+), 14 deletions(-) diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h index 60e6e3d..92ec765 100644 --- a/drivers/infiniband/core/uverbs.h +++ b/drivers/infiniband/core/uverbs.h @@ -85,7 +85,7 @@ */ struct ib_uverbs_device { - struct kref ref; + atomic_t refcount; int num_comp_vectors; struct completion comp; struct device *dev; @@ -94,6 +94,7 @@ struct ib_uverbs_device { struct cdev cdev; struct rb_root xrcd_tree; struct mutex xrcd_tree_mutex; + struct kobject kobj; }; struct ib_uverbs_event_file { diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c index c238eba..9f39978 100644 --- a/drivers/infiniband/core/uverbs_main.c +++ b/drivers/infiniband/core/uverbs_main.c @@ -130,14 +130,18 @@ static int (*uverbs_ex_cmd_table[])(struct ib_uverbs_file *file, static void ib_uverbs_add_one(struct ib_device *device); static void ib_uverbs_remove_one(struct ib_device *device); -static void ib_uverbs_release_dev(struct kref *ref) +static void ib_uverbs_release_dev(struct kobject *kobj) { struct ib_uverbs_device *dev = - container_of(ref, struct ib_uverbs_device, ref); + container_of(kobj, struct ib_uverbs_device, kobj); - complete(&dev->comp); + kfree(dev); } +static struct kobj_type ib_uverbs_dev_ktype = { + .release = ib_uverbs_release_dev, +}; + static void ib_uverbs_release_event_file(struct kref *ref) { struct ib_uverbs_event_file *file = @@ -303,13 +307,19 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file, return context->device->dealloc_ucontext(context); } +static void ib_uverbs_comp_dev(struct ib_uverbs_device *dev) +{ + complete(&dev->comp); +} + static void ib_uverbs_release_file(struct kref *ref) { struct ib_uverbs_file *file = container_of(ref, struct ib_uverbs_file, ref); module_put(file->device->ib_dev->owner); - kref_put(&file->device->ref, ib_uverbs_release_dev); + if (atomic_dec_and_test(&file->device->refcount)) + ib_uverbs_comp_dev(file->device); kfree(file); } @@ -775,9 +785,7 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp) int ret; dev = container_of(inode->i_cdev, struct ib_uverbs_device, cdev); - if (dev) - kref_get(&dev->ref); - else + if (!atomic_inc_not_zero(&dev->refcount)) return -ENXIO; if (!try_module_get(dev->ib_dev->owner)) { @@ -798,6 +806,7 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp) mutex_init(&file->mutex); filp->private_data = file; + kobject_get(&dev->kobj); return nonseekable_open(inode, filp); @@ -805,13 +814,16 @@ err_module: module_put(dev->ib_dev->owner); err: - kref_put(&dev->ref, ib_uverbs_release_dev); + if (atomic_dec_and_test(&dev->refcount)) + ib_uverbs_comp_dev(dev); + return ret; } static int ib_uverbs_close(struct inode *inode, struct file *filp) { struct ib_uverbs_file *file = filp->private_data; + struct ib_uverbs_device *dev = file->device; ib_uverbs_cleanup_ucontext(file, file->ucontext); @@ -819,6 +831,7 @@ static int ib_uverbs_close(struct inode *inode, struct file *filp) kref_put(&file->async_file->ref, ib_uverbs_release_event_file); kref_put(&file->ref, ib_uverbs_release_file); + kobject_put(&dev->kobj); return 0; } @@ -914,10 +927,11 @@ static void ib_uverbs_add_one(struct ib_device *device) if (!uverbs_dev) return; - kref_init(&uverbs_dev->ref); + atomic_set(&uverbs_dev->refcount, 1); init_completion(&uverbs_dev->comp); uverbs_dev->xrcd_tree = RB_ROOT; mutex_init(&uverbs_dev->xrcd_tree_mutex); + kobject_init(&uverbs_dev->kobj, &ib_uverbs_dev_ktype); spin_lock(&map_lock); devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES); @@ -944,6 +958,7 @@ static void ib_uverbs_add_one(struct ib_device *device) cdev_init(&uverbs_dev->cdev, NULL); uverbs_dev->cdev.owner = THIS_MODULE; uverbs_dev->cdev.ops = device->mmap ? &uverbs_mmap_fops : &uverbs_fops; + uverbs_dev->cdev.kobj.parent = &uverbs_dev->kobj; kobject_set_name(&uverbs_dev->cdev.kobj, "uverbs%d", uverbs_dev->devnum); if (cdev_add(&uverbs_dev->cdev, base, 1)) goto err_cdev; @@ -974,9 +989,10 @@ err_cdev: clear_bit(devnum, overflow_map); err: - kref_put(&uverbs_dev->ref, ib_uverbs_release_dev); + if (atomic_dec_and_test(&uverbs_dev->refcount)) + ib_uverbs_comp_dev(uverbs_dev); wait_for_completion(&uverbs_dev->comp); - kfree(uverbs_dev); + kobject_put(&uverbs_dev->kobj); return; } @@ -996,9 +1012,10 @@ static void ib_uverbs_remove_one(struct ib_device *device) else clear_bit(uverbs_dev->devnum - IB_UVERBS_MAX_DEVICES, overflow_map); - kref_put(&uverbs_dev->ref, ib_uverbs_release_dev); + if (atomic_dec_and_test(&uverbs_dev->refcount)) + ib_uverbs_comp_dev(uverbs_dev); wait_for_completion(&uverbs_dev->comp); - kfree(uverbs_dev); + kobject_put(&uverbs_dev->kobj); } static char *uverbs_devnode(struct device *dev, umode_t *mode)