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>

diff --git a/drivers/staging/rdma/hfi1/mmu_rb.c b/drivers/staging/rdma/hfi1/mmu_rb.c
index 648f7e0a1d1716f758a1c28631500708969c6225..f42a33b55dc4f82acb747472cbb9f2328ff490ce 100644 (file)
--- 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);