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authorYishai Hadas <yishaih@mellanox.com>2015-08-13 18:32:03 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-10-01 12:07:33 +0200
commitcaf233503f3ce58ebe564c5d11aa53f2344a1053 (patch)
treec95678ea8d33560fbeb0c093c8a3bcf24bb19283
parent939f8043048f59a4d77db1f5eeed1526a74a1503 (diff)
downloadlinux-linaro-stable-caf233503f3ce58ebe564c5d11aa53f2344a1053.tar.gz
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.h3
-rw-r--r--drivers/infiniband/core/uverbs_main.c43
2 files changed, 32 insertions, 14 deletions
diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
index 0fcd7aa26fa2..8b8de21bfdc5 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 949b38633496..b6062b9236a2 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -119,14 +119,18 @@ 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 =
@@ -282,13 +286,19 @@ 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);
}
@@ -629,9 +639,7 @@ 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)) {
@@ -652,6 +660,7 @@ 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);
@@ -659,13 +668,16 @@ 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);
@@ -673,6 +685,7 @@ 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;
}
@@ -768,10 +781,11 @@ 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);
@@ -798,6 +812,7 @@ 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;
@@ -828,9 +843,10 @@ 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;
}
@@ -850,9 +866,10 @@ 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)