From 4b00d9490f2147d29f107f36391b0cc77bcd944f Mon Sep 17 00:00:00 2001
From: Mitko Haralanov <mitko.haralanov@intel.com>
Date: Tue, 8 Mar 2016 11:14:31 -0800
Subject: [PATCH] IB/hfi1: Prevent NULL pointer dereference

Prevent a potential NULL pointer dereference (found
by code inspection) when unregistering an MMU handler.

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Reviewed-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Mitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: Jubin John <jubin.john@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
---
 drivers/staging/rdma/hfi1/mmu_rb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/staging/rdma/hfi1/mmu_rb.c b/drivers/staging/rdma/hfi1/mmu_rb.c
index 648f7e0a1d17..f42a33b55dc4 100644
--- a/drivers/staging/rdma/hfi1/mmu_rb.c
+++ b/drivers/staging/rdma/hfi1/mmu_rb.c
@@ -107,6 +107,9 @@ void hfi1_mmu_rb_unregister(struct rb_root *root)
 	struct mmu_rb_handler *handler = find_mmu_handler(root);
 	unsigned long flags;
 
+	if (!handler)
+		return;
+
 	spin_lock_irqsave(&mmu_rb_lock, flags);
 	list_del(&handler->list);
 	spin_unlock_irqrestore(&mmu_rb_lock, flags);
-- 
2.20.1