[PATCH v2] IB core: Fix locking on device numbers allocation

[Eli Cohen <eli-VPRAkNaXOzVS1MOuV/RT9w@public.gmane.org>]

When the driver needs to dynamically allocate char device numbers in systems
with more than IB_UVERBS_MAX_DEVICES devices, it releases map lock, allocates a
new range and a new device number from that range, and only then re-acquires
the lock. This must be protected for the same reasoning that the map_lock
spinlock is used. Without protecting we could also end up calling
alloc_chrdev_region() a nubmer of times and cause a leakage. Fix this by
replacing map_lock with a mutex and apply on the all the allocation code.

Signed-off-by: Eli Cohen <eli-VPRAkNaXOzVS1MOuV/RT9w@public.gmane.org>
---
Changes from previous version:
Protect with the mutex the clear_bit on the map allocations.


 drivers/infiniband/core/uverbs_main.c |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index d805cf3..a16d90d 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -72,7 +72,7 @@ DEFINE_IDR(ib_uverbs_cq_idr);
 DEFINE_IDR(ib_uverbs_qp_idr);
 DEFINE_IDR(ib_uverbs_srq_idr);
 
-static DEFINE_SPINLOCK(map_lock);
+static DEFINE_MUTEX(map_lock);
 static DECLARE_BITMAP(dev_map, IB_UVERBS_MAX_DEVICES);
 
 static ssize_t (*uverbs_cmd_table[])(struct ib_uverbs_file *file,
@@ -738,15 +738,15 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	kref_init(&uverbs_dev->ref);
 	init_completion(&uverbs_dev->comp);
 
-	spin_lock(&map_lock);
+	mutex_lock(&map_lock);
 	devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
 	if (devnum >= IB_UVERBS_MAX_DEVICES) {
-		spin_unlock(&map_lock);
 		devnum = find_overflow_devnum();
-		if (devnum < 0)
+		if (devnum < 0) {
+			mutex_unlock(&map_lock);
 			goto err;
+		}
 
-		spin_lock(&map_lock);
 		uverbs_dev->devnum = devnum + IB_UVERBS_MAX_DEVICES;
 		base = devnum + overflow_maj;
 		set_bit(devnum, overflow_map);
@@ -755,7 +755,7 @@ static void ib_uverbs_add_one(struct ib_device *device)
 		base = devnum + IB_UVERBS_BASE_DEV;
 		set_bit(devnum, dev_map);
 	}
-	spin_unlock(&map_lock);
+	mutex_unlock(&map_lock);
 
 	uverbs_dev->ib_dev           = device;
 	uverbs_dev->num_comp_vectors = device->num_comp_vectors;
@@ -787,10 +787,12 @@ err_class:
 
 err_cdev:
 	cdev_del(&uverbs_dev->cdev);
+	mutex_lock(&map_lock);
 	if (uverbs_dev->devnum < IB_UVERBS_MAX_DEVICES)
 		clear_bit(devnum, dev_map);
 	else
 		clear_bit(devnum, overflow_map);
+	mutex_unlock(&map_lock);
 
 err:
 	kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);
@@ -810,10 +812,12 @@ static void ib_uverbs_remove_one(struct ib_device *device)
 	device_destroy(uverbs_class, uverbs_dev->cdev.dev);
 	cdev_del(&uverbs_dev->cdev);
 
+	mutex_lock(&map_lock);
 	if (uverbs_dev->devnum < IB_UVERBS_MAX_DEVICES)
 		clear_bit(uverbs_dev->devnum, dev_map);
 	else
 		clear_bit(uverbs_dev->devnum - IB_UVERBS_MAX_DEVICES, overflow_map);
+	mutex_unlock(&map_lock);
 
 	kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);
 	wait_for_completion(&uverbs_dev->comp);
-- 
1.7.0.3

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