tg3: Fix vunmap() BUG_ON() triggered from tg3_free_consistent().

tg3_free_consistent() calls dma_free_coherent() to free tp->hw_stats
under spinlock and can trigger BUG_ON() in vunmap() because vunmap()
may sleep.  Fix it by removing the spinlock and relying on the
TG3_FLAG_INIT_COMPLETE flag to prevent race conditions between
tg3_get_stats64() and tg3_free_consistent().  TG3_FLAG_INIT_COMPLETE
is always cleared under tp->lock before tg3_free_consistent()
and therefore tg3_get_stats64() can safely access tp->hw_stats
under tp->lock if TG3_FLAG_INIT_COMPLETE is set.

Fixes: f5992b72ebe0 ("tg3: Fix race condition in tg3_get_stats64().")
Reported-by: Zumeng Chen <zumeng.chen@gmail.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index 08bbb639be1a5ab3bc10ea27b31df88cb6d2b569..9f59b1270a7c68da3086d22db2930d041cbaaec8 100644 (file)
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -8733,14 +8733,15 @@ static void tg3_free_consistent(struct tg3 *tp)
        tg3_mem_rx_release(tp);
        tg3_mem_tx_release(tp);
 
-       /* Protect tg3_get_stats64() from reading freed tp->hw_stats. */
-       tg3_full_lock(tp, 0);
+       /* tp->hw_stats can be referenced safely:
+        *     1. under rtnl_lock
+        *     2. or under tp->lock if TG3_FLAG_INIT_COMPLETE is set.
+        */
        if (tp->hw_stats) {
                dma_free_coherent(&tp->pdev->dev, sizeof(struct tg3_hw_stats),
                                  tp->hw_stats, tp->stats_mapping);
                tp->hw_stats = NULL;
        }
-       tg3_full_unlock(tp);
 }
 
 /*
@@ -14178,7 +14179,7 @@ static void tg3_get_stats64(struct net_device *dev,
        struct tg3 *tp = netdev_priv(dev);
 
        spin_lock_bh(&tp->lock);
-       if (!tp->hw_stats) {
+       if (!tp->hw_stats || !tg3_flag(tp, INIT_COMPLETE)) {
                *stats = tp->net_stats_prev;
                spin_unlock_bh(&tp->lock);
                return;