[PATCH 4.15 005/146] IB/uverbs: Improve lockdep_check

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>

commit 104f268d439b3c21c83708e52946a4d8d37f3d0f upstream.

This is really being used as an assert that the expected usecnt
is being held and implicitly that the usecnt is valid. Rename it to
assert_uverbs_usecnt and tighten the checks to only accept valid
values of usecnt (eg 0 and < -1 are invalid).

The tigher checkes make the assertion cover more cases and is more
likely to find bugs via syzkaller/etc.

Fixes: 3832125624b7 ("IB/core: Add support for idr types")
Signed-off-by: Leon Romanovsky <leon@xxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/infiniband/core/rdma_core.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/drivers/infiniband/core/rdma_core.c
+++ b/drivers/infiniband/core/rdma_core.c
@@ -407,13 +407,13 @@ static int __must_check remove_commit_fd
 	return ret;
 }
 
-static void lockdep_check(struct ib_uobject *uobj, bool exclusive)
+static void assert_uverbs_usecnt(struct ib_uobject *uobj, bool exclusive)
 {
 #ifdef CONFIG_LOCKDEP
 	if (exclusive)
-		WARN_ON(atomic_read(&uobj->usecnt) > 0);
+		WARN_ON(atomic_read(&uobj->usecnt) != -1);
 	else
-		WARN_ON(atomic_read(&uobj->usecnt) == -1);
+		WARN_ON(atomic_read(&uobj->usecnt) <= 0);
 #endif
 }
 
@@ -452,7 +452,7 @@ int __must_check rdma_remove_commit_uobj
 		WARN(true, "ib_uverbs: Cleanup is running while removing an uobject\n");
 		return 0;
 	}
-	lockdep_check(uobj, true);
+	assert_uverbs_usecnt(uobj, true);
 	ret = _rdma_remove_commit_uobject(uobj, RDMA_REMOVE_DESTROY);
 
 	up_read(&ucontext->cleanup_rwsem);
@@ -482,7 +482,7 @@ int rdma_explicit_destroy(struct ib_uobj
 		WARN(true, "ib_uverbs: Cleanup is running while removing an uobject\n");
 		return 0;
 	}
-	lockdep_check(uobject, true);
+	assert_uverbs_usecnt(uobject, true);
 	ret = uobject->type->type_class->remove_commit(uobject,
 						       RDMA_REMOVE_DESTROY);
 	if (ret)
@@ -569,7 +569,7 @@ static void lookup_put_fd_uobject(struct
 
 void rdma_lookup_put_uobject(struct ib_uobject *uobj, bool exclusive)
 {
-	lockdep_check(uobj, exclusive);
+	assert_uverbs_usecnt(uobj, exclusive);
 	uobj->type->type_class->lookup_put(uobj, exclusive);
 	/*
 	 * In order to unlock an object, either decrease its usecnt for