[IB] uverbs: Close some exploitable races

Al Viro pointed out that the current IB userspace verbs interface
allows userspace to cause mischief by closing file descriptors before
we're ready, or issuing the same command twice at the same time.  This
patch closes those races, and fixes other obvious problems such as a
module reference leak.

Some other interface bogosities will require an ABI change to fix
properly, so I'm deferring those fixes until 2.6.15.

Signed-off-by: Roland Dreier <rolandd@cisco.com>

3 files changed, 86 insertions, 62 deletions

diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
index b1897bed14ad..cc124344dd2c 100644
--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -69,6 +69,7 @@ struct ib_uverbs_event_file {
 
 struct ib_uverbs_file {
 	struct kref				ref;
+	struct semaphore			mutex;
 	struct ib_uverbs_device		       *device;
 	struct ib_ucontext		       *ucontext;
 	struct ib_event_handler			event_handler;
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index e91ebde46481..562445165d2b 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -76,8 +76,9 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 	struct ib_uverbs_get_context_resp resp;
 	struct ib_udata                   udata;
 	struct ib_device                 *ibdev = file->device->ib_dev;
+	struct ib_ucontext		 *ucontext;
 	int i;
-	int ret = in_len;
+	int ret;
 
 	if (out_len < sizeof resp)
 		return -ENOSPC;
@@ -85,45 +86,56 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 	if (copy_from_user(&cmd, buf, sizeof cmd))
 		return -EFAULT;
 
+	down(&file->mutex);
+
+	if (file->ucontext) {
+		ret = -EINVAL;
+		goto err;
+	}
+
 	INIT_UDATA(&udata, buf + sizeof cmd,
 		   (unsigned long) cmd.response + sizeof resp,
 		   in_len - sizeof cmd, out_len - sizeof resp);
 
-	file->ucontext = ibdev->alloc_ucontext(ibdev, &udata);
-	if (IS_ERR(file->ucontext)) {
-		ret = PTR_ERR(file->ucontext);
-		file->ucontext = NULL;
-		return ret;
-	}
+	ucontext = ibdev->alloc_ucontext(ibdev, &udata);
+	if (IS_ERR(ucontext))
+		return PTR_ERR(file->ucontext);
 
-	file->ucontext->device = ibdev;
-	INIT_LIST_HEAD(&file->ucontext->pd_list);
-	INIT_LIST_HEAD(&file->ucontext->mr_list);
-	INIT_LIST_HEAD(&file->ucontext->mw_list);
-	INIT_LIST_HEAD(&file->ucontext->cq_list);
-	INIT_LIST_HEAD(&file->ucontext->qp_list);
-	INIT_LIST_HEAD(&file->ucontext->srq_list);
-	INIT_LIST_HEAD(&file->ucontext->ah_list);
-	spin_lock_init(&file->ucontext->lock);
+	ucontext->device = ibdev;
+	INIT_LIST_HEAD(&ucontext->pd_list);
+	INIT_LIST_HEAD(&ucontext->mr_list);
+	INIT_LIST_HEAD(&ucontext->mw_list);
+	INIT_LIST_HEAD(&ucontext->cq_list);
+	INIT_LIST_HEAD(&ucontext->qp_list);
+	INIT_LIST_HEAD(&ucontext->srq_list);
+	INIT_LIST_HEAD(&ucontext->ah_list);
 
 	resp.async_fd = file->async_file.fd;
 	for (i = 0; i < file->device->num_comp; ++i)
 		if (copy_to_user((void __user *) (unsigned long) cmd.cq_fd_tab +
 				 i * sizeof (__u32),
-				 &file->comp_file[i].fd, sizeof (__u32)))
-			goto err;
+				 &file->comp_file[i].fd, sizeof (__u32))) {
+			ret = -EFAULT;
+			goto err_free;
+		}
 
 	if (copy_to_user((void __user *) (unsigned long) cmd.response,
-			 &resp, sizeof resp))
-		goto err;
+			 &resp, sizeof resp)) {
+		ret = -EFAULT;
+		goto err_free;
+	}
+
+	file->ucontext = ucontext;
+	up(&file->mutex);
 
 	return in_len;
 
-err:
-	ibdev->dealloc_ucontext(file->ucontext);
-	file->ucontext = NULL;
+err_free:
+	ibdev->dealloc_ucontext(ucontext);
 
-	return -EFAULT;
+err:
+	up(&file->mutex);
+	return ret;
 }
 
 ssize_t ib_uverbs_query_device(struct ib_uverbs_file *file,
@@ -352,9 +364,9 @@ retry:
 	if (ret)
 		goto err_pd;
 
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_add_tail(&uobj->list, &file->ucontext->pd_list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	memset(&resp, 0, sizeof resp);
 	resp.pd_handle = uobj->id;
@@ -368,9 +380,9 @@ retry:
 	return in_len;
 
 err_list:
- 	spin_lock_irq(&file->ucontext->lock);
+ 	down(&file->mutex);
 	list_del(&uobj->list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	down(&ib_uverbs_idr_mutex);
 	idr_remove(&ib_uverbs_pd_idr, uobj->id);
@@ -410,9 +422,9 @@ ssize_t ib_uverbs_dealloc_pd(struct ib_uverbs_file *file,
 
 	idr_remove(&ib_uverbs_pd_idr, cmd.pd_handle);
 
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_del(&uobj->list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	kfree(uobj);
 
@@ -512,9 +524,9 @@ retry:
 
 	resp.mr_handle = obj->uobject.id;
 
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_add_tail(&obj->uobject.list, &file->ucontext->mr_list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	if (copy_to_user((void __user *) (unsigned long) cmd.response,
 			 &resp, sizeof resp)) {
@@ -527,9 +539,9 @@ retry:
 	return in_len;
 
 err_list:
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_del(&obj->uobject.list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 err_unreg:
 	ib_dereg_mr(mr);
@@ -570,9 +582,9 @@ ssize_t ib_uverbs_dereg_mr(struct ib_uverbs_file *file,
 
 	idr_remove(&ib_uverbs_mr_idr, cmd.mr_handle);
 
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_del(&memobj->uobject.list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	ib_umem_release(file->device->ib_dev, &memobj->umem);
 	kfree(memobj);
@@ -647,9 +659,9 @@ retry:
 	if (ret)
 		goto err_cq;
 
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_add_tail(&uobj->uobject.list, &file->ucontext->cq_list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	memset(&resp, 0, sizeof resp);
 	resp.cq_handle = uobj->uobject.id;
@@ -664,9 +676,9 @@ retry:
 	return in_len;
 
 err_list:
- 	spin_lock_irq(&file->ucontext->lock);
+ 	down(&file->mutex);
 	list_del(&uobj->uobject.list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	down(&ib_uverbs_idr_mutex);
 	idr_remove(&ib_uverbs_cq_idr, uobj->uobject.id);
@@ -712,9 +724,9 @@ ssize_t ib_uverbs_destroy_cq(struct ib_uverbs_file *file,
 
 	idr_remove(&ib_uverbs_cq_idr, cmd.cq_handle);
 
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_del(&uobj->uobject.list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	spin_lock_irq(&file->comp_file[0].lock);
 	list_for_each_entry_safe(evt, tmp, &uobj->comp_list, obj_list) {
@@ -847,9 +859,9 @@ retry:
 
 	resp.qp_handle = uobj->uobject.id;
 
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_add_tail(&uobj->uobject.list, &file->ucontext->qp_list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	if (copy_to_user((void __user *) (unsigned long) cmd.response,
 			 &resp, sizeof resp)) {
@@ -862,9 +874,9 @@ retry:
 	return in_len;
 
 err_list:
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_del(&uobj->uobject.list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 err_destroy:
 	ib_destroy_qp(qp);
@@ -989,9 +1001,9 @@ ssize_t ib_uverbs_destroy_qp(struct ib_uverbs_file *file,
 
 	idr_remove(&ib_uverbs_qp_idr, cmd.qp_handle);
 
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_del(&uobj->uobject.list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	spin_lock_irq(&file->async_file.lock);
 	list_for_each_entry_safe(evt, tmp, &uobj->event_list, obj_list) {
@@ -1136,9 +1148,9 @@ retry:
 
 	resp.srq_handle = uobj->uobject.id;
 
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_add_tail(&uobj->uobject.list, &file->ucontext->srq_list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	if (copy_to_user((void __user *) (unsigned long) cmd.response,
 			 &resp, sizeof resp)) {
@@ -1151,9 +1163,9 @@ retry:
 	return in_len;
 
 err_list:
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_del(&uobj->uobject.list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 err_destroy:
 	ib_destroy_srq(srq);
@@ -1227,9 +1239,9 @@ ssize_t ib_uverbs_destroy_srq(struct ib_uverbs_file *file,
 
 	idr_remove(&ib_uverbs_srq_idr, cmd.srq_handle);
 
-	spin_lock_irq(&file->ucontext->lock);
+	down(&file->mutex);
 	list_del(&uobj->uobject.list);
-	spin_unlock_irq(&file->ucontext->lock);
+	up(&file->mutex);
 
 	spin_lock_irq(&file->async_file.lock);
 	list_for_each_entry_safe(evt, tmp, &uobj->event_list, obj_list) {
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index ce5bdb7af306..12511808de21 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -448,7 +448,9 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 	if (hdr.in_words * 4 != count)
 		return -EINVAL;
 
-	if (hdr.command < 0 || hdr.command >= ARRAY_SIZE(uverbs_cmd_table))
+	if (hdr.command < 0				||
+	    hdr.command >= ARRAY_SIZE(uverbs_cmd_table) ||
+	    !uverbs_cmd_table[hdr.command])
 		return -EINVAL;
 
 	if (!file->ucontext                               &&
@@ -484,27 +486,29 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
 	file = kmalloc(sizeof *file +
 		       (dev->num_comp - 1) * sizeof (struct ib_uverbs_event_file),
 		       GFP_KERNEL);
-	if (!file)
-		return -ENOMEM;
+	if (!file) {
+		ret = -ENOMEM;
+		goto err;
+	}
 
 	file->device = dev;
 	kref_init(&file->ref);
+	init_MUTEX(&file->mutex);
 
 	file->ucontext = NULL;
 
+	kref_get(&file->ref);
 	ret = ib_uverbs_event_init(&file->async_file, file);
 	if (ret)
-		goto err;
+		goto err_kref;
 
 	file->async_file.is_async = 1;
 
-	kref_get(&file->ref);
-
 	for (i = 0; i < dev->num_comp; ++i) {
+		kref_get(&file->ref);
 		ret = ib_uverbs_event_init(&file->comp_file[i], file);
 		if (ret)
 			goto err_async;
-		kref_get(&file->ref);
 		file->comp_file[i].is_async = 0;
 	}
 
@@ -524,9 +528,16 @@ err_async:
 
 	ib_uverbs_event_release(&file->async_file);
 
-err:
+err_kref:
+	/*
+	 * One extra kref_put() because we took a reference before the
+	 * event file creation that failed and got us here.
+	 */
+	kref_put(&file->ref, ib_uverbs_release_file);
 	kref_put(&file->ref, ib_uverbs_release_file);
 
+err:
+	module_put(dev->ib_dev->owner);
 	return ret;
 }