[PATCH 4.14 22/89] IB/hfi1: Prevent a NULL dereference

[Greg Kroah-Hartman]

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

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

From: Dan Carpenter <dan.carpen...@oracle.com>

commit 57194fa763bfa1a0908f30d4c77835beaa118fcb upstream.

In the original code, we set "fd->uctxt" to NULL and then dereference it
which will cause an Oops.

Fixes: f2a3bc00a03c ("IB/hfi1: Protect context array set/clear with spinlock")
Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>
Reviewed-by: Michael J. Ruhl <michael.j.r...@intel.com>
Signed-off-by: Doug Ledford <dledf...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/infiniband/hw/hfi1/file_ops.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/hw/hfi1/file_ops.c
+++ b/drivers/infiniband/hw/hfi1/file_ops.c
@@ -881,11 +881,11 @@ static int complete_subctxt(struct hfi1_
        }
 
        if (ret) {
-               hfi1_rcd_put(fd->uctxt);
-               fd->uctxt = NULL;
                spin_lock_irqsave(&fd->dd->uctxt_lock, flags);
                __clear_bit(fd->subctxt, fd->uctxt->in_use_ctxts);
                spin_unlock_irqrestore(&fd->dd->uctxt_lock, flags);
+               hfi1_rcd_put(fd->uctxt);
+               fd->uctxt = NULL;
        }
 
        return ret;