diff options
author | Yishai Hadas <yishaih@mellanox.com> | 2015-08-13 18:32:03 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-09-29 19:33:35 +0200 |
commit | a5b06eff5864b8bbe56cb38a3a986909cc4f9836 (patch) | |
tree | af8bce2e7a329e002d782f22c4b5085462677c5a | |
parent | 2cc11121795fecafd75a1d6f79ef95713729fdbf (diff) | |
download | lwn-a5b06eff5864b8bbe56cb38a3a986909cc4f9836.tar.gz lwn-a5b06eff5864b8bbe56cb38a3a986909cc4f9836.zip |
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 <yishaih@mellanox.com>
Signed-off-by: Shachar Raindel <raindel@mellanox.com>
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | drivers/infiniband/core/uverbs.h | 3 | ||||
-rw-r--r-- | 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 ba365b6d1e8d..65cbfcc92f11 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 f6eef2da7097..15f4126a577d 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); } @@ -743,9 +753,7 @@ 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)) { @@ -766,6 +774,7 @@ 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); @@ -773,13 +782,16 @@ 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); @@ -787,6 +799,7 @@ 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; } @@ -882,10 +895,11 @@ 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); @@ -912,6 +926,7 @@ 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; @@ -942,9 +957,10 @@ 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; } @@ -964,9 +980,10 @@ 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) |