linux-kernel - [PATCH 4.14 079/496] IB/uverbs: Fix unbalanced unlock on error path for rdma_explicit

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Date:   Mon, 28 May 2018 11:57:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Leon Romanovsky <leon@...nel.org>,
        Dennis Dalessandro <dennis.dalessandro@...el.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.14 079/496] IB/uverbs: Fix unbalanced unlock on error path for rdma_explicit_destroy

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

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

From: Jason Gunthorpe <jgg@...lanox.com>

[ Upstream commit ec6f8401c48a86809237e86878a6fac6b281118f ]

If remove_commit fails then the lock is left locked while the uobj still
exists. Eventually the kernel will deadlock.

lockdep detects this and says:

 test/4221 is leaving the kernel with locks still held!
 1 lock held by test/4221:
  #0:  (&ucontext->cleanup_rwsem){.+.+}, at: [<000000001e5c7523>] rdma_explicit_destroy+0x37/0x120 [ib_uverbs]

Fixes: 4da70da23e9b ("IB/core: Explicitly destroy an object while keeping uobject")
Signed-off-by: Leon Romanovsky <leon@...nel.org>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@...el.com>
Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/infiniband/core/rdma_core.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/core/rdma_core.c
+++ b/drivers/infiniband/core/rdma_core.c
@@ -486,12 +486,13 @@ int rdma_explicit_destroy(struct ib_uobj
 	ret = uobject->type->type_class->remove_commit(uobject,
 						       RDMA_REMOVE_DESTROY);
 	if (ret)
-		return ret;
+		goto out;
 
 	uobject->type = &null_obj_type;
 
+out:
 	up_read(&ucontext->cleanup_rwsem);
-	return 0;
+	return ret;
 }
 
 static void alloc_commit_idr_uobject(struct ib_uobject *uobj)