[PATCH 4.4 34/72] RDMA/ucma: Check that device exists prior to accessing it

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

From: Leon Romanovsky <leonro@mellanox.com>

commit c8d3bcbfc5eab3f01cf373d039af725f3b488813 upstream.

Ensure that device exists prior to accessing its properties.

Reported-by: <syzbot+71655d44855ac3e76366@syzkaller.appspotmail.com>
Fixes: 75216638572f ("RDMA/cma: Export rdma cm interface to userspace")
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/infiniband/core/ucma.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -1316,7 +1316,7 @@ static ssize_t ucma_notify(struct ucma_f
 {
 	struct rdma_ucm_notify cmd;
 	struct ucma_context *ctx;
-	int ret;
+	int ret = -EINVAL;
 
 	if (copy_from_user(&cmd, inbuf, sizeof(cmd)))
 		return -EFAULT;
@@ -1325,7 +1325,9 @@ static ssize_t ucma_notify(struct ucma_f
 	if (IS_ERR(ctx))
 		return PTR_ERR(ctx);
 
-	ret = rdma_notify(ctx->cm_id, (enum ib_event_type) cmd.event);
+	if (ctx->cm_id->device)
+		ret = rdma_notify(ctx->cm_id, (enum ib_event_type)cmd.event);
+
 	ucma_put_ctx(ctx);
 	return ret;
 }