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IB/uverbs: Fix race between ib_uverbs_open and remove_one

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Fixes: 2a72f21226 ("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>
This commit is contained in:
Yishai Hadas 2015-08-13 18:32:03 +03:00 committed by Doug Ledford
parent 03c40442a0
commit 35d4a0b63d
2 changed files with 32 additions and 14 deletions
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3
drivers/infiniband/core/uverbs.h
View File

@ -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 {

43
drivers/infiniband/core/uverbs_main.c
View File

@ -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, void *client_data);
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 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
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 @@ static void ib_uverbs_add_one(struct ib_device *device)
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, void *client_data)
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)