bna: Eliminate Small Race Condition Window in RX Path

Change details:
 - In a continuous sequence of ifconfig up/down operations, there is a small
   window of race between bnad_set_rx_mode() and bnad_cleanup_rx() while the
   former tries to access rx_info->rx & the latter sets it to NULL. This race
   could lead to bna_rx_mode_set() being called with a NULL (rx_info->rx)
   pointer and a crash.
 - Hold bnad->bna_lock while setting / unsetting rx_info->rx in bnad_setup_rx()
   & bnad_cleanup_rx(), thereby eliminating the race described above.

Signed-off-by: Gurunatha Karaje <gkaraje@brocade.com>
Signed-off-by: Rasesh Mody <rmody@brocade.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/net/ethernet/brocade/bna/bnad.c b/drivers/net/ethernet/brocade/bna/bnad.c
index 33ab1f81c1c2..abca1399fe51 100644
--- a/drivers/net/ethernet/brocade/bna/bnad.c
+++ b/drivers/net/ethernet/brocade/bna/bnad.c
@@ -1875,10 +1875,10 @@ bnad_cleanup_rx(struct bnad *bnad, u32 rx_id)
 
         spin_lock_irqsave(&bnad->bna_lock, flags);
         bna_rx_destroy(rx_info->rx);
-        spin_unlock_irqrestore(&bnad->bna_lock, flags);
 
         rx_info->rx = NULL;
         rx_info->rx_id = 0;
+        spin_unlock_irqrestore(&bnad->bna_lock, flags);
 
         bnad_rx_res_free(bnad, res_info);
 }
@@ -1932,12 +1932,13 @@ bnad_setup_rx(struct bnad *bnad, u32 rx_id)
         spin_lock_irqsave(&bnad->bna_lock, flags);
         rx = bna_rx_create(&bnad->bna, bnad, rx_config, &rx_cbfn, res_info,
                         rx_info);
-        spin_unlock_irqrestore(&bnad->bna_lock, flags);
         if (!rx) {
                 err = -ENOMEM;
+                spin_unlock_irqrestore(&bnad->bna_lock, flags);
                 goto err_return;
         }
         rx_info->rx = rx;
+        spin_unlock_irqrestore(&bnad->bna_lock, flags);
 
         /*
          * Init NAPI, so that state is set to NAPI_STATE_SCHED,