From: Yishai Hadas Date: Thu, 13 Aug 2015 15:32:03 +0000 (+0300) Subject: IB/uverbs: Fix race between ib_uverbs_open and remove_one X-Git-Tag: v3.2.72~50 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=cf50958a5affdc35f664b82c79d650cc9c83d499 IB/uverbs: Fix race between ib_uverbs_open and remove_one commit 35d4a0b63dc0c6d1177d4f532a9deae958f0662c upstream. 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 Signed-off-by: Doug Ledford Signed-off-by: Ben Hutchings --- diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h index 5bcb2afd3dcb..228af1894dc9 100644 --- a/drivers/infiniband/core/uverbs.h +++ b/drivers/infiniband/core/uverbs.h @@ -69,7 +69,7 @@ */ struct ib_uverbs_device { - struct kref ref; + atomic_t refcount; int num_comp_vectors; struct completion comp; struct device *dev; @@ -78,6 +78,7 @@ 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 9379b97cdecb..f07c6e317771 100644 --- a/drivers/infiniband/core/uverbs_main.c +++ b/drivers/infiniband/core/uverbs_main.c @@ -117,14 +117,18 @@ static ssize_t (*uverbs_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 = @@ -273,13 +277,19 @@ 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); } @@ -621,9 +631,7 @@ 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)) { @@ -644,6 +652,7 @@ 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); @@ -651,13 +660,16 @@ 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); @@ -665,6 +677,7 @@ 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; } @@ -760,10 +773,11 @@ 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); @@ -790,6 +804,7 @@ 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; @@ -820,9 +835,10 @@ 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; } @@ -842,9 +858,10 @@ 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, mode_t *mode)