fm10k: prevent null pointer dereference of msix_entries table

According to the C standard dereferencing a variable before it is
checked invokes undefined behavior, and thus compilers are free to
assume the check for NULL isn't necessary. Prevent this by re-ordering
the NULL check of msix_entries in fm10k_free_mbx_irq.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <Krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_pci.c b/drivers/net/ethernet/intel/fm10k/fm10k_pci.c
index 6190a81..8c23fb3 100644 (file)
--- a/drivers/net/ethernet/intel/fm10k/fm10k_pci.c
+++ b/drivers/net/ethernet/intel/fm10k/fm10k_pci.c
@@ -1143,14 +1143,16 @@ static irqreturn_t fm10k_msix_mbx_pf(int __always_unused irq, void *data)
 
 void fm10k_mbx_free_irq(struct fm10k_intfc *interface)
 {
-       struct msix_entry *entry = &interface->msix_entries[FM10K_MBX_VECTOR];
        struct fm10k_hw *hw = &interface->hw;
+       struct msix_entry *entry;
        int itr_reg;
 
        /* no mailbox IRQ to free if MSI-X is not enabled */
        if (!interface->msix_entries)
                return;
 
+       entry = &interface->msix_entries[FM10K_MBX_VECTOR];
+
        /* disconnect the mailbox */
        hw->mbx.ops.disconnect(hw, &hw->mbx);