[PATCH 4.14 29/45] tg3: Fix vunmap() BUG_ON() triggered from tg3_free_consistent().

Greg Kroah-Hartman
2018-05-18T08:15:46Z

From: Michael Chan <michael.chan@broadcom.com>

[ Upstream commit d89a2adb8bfe6f8949ff389acdb9fa298b6e8e12 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/broadcom/tg3.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -8723,14 +8723,15 @@ static void tg3_free_consistent(struct t
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);
}

/*
@@ -14167,7 +14168,7 @@ static void tg3_get_stats64(struct net_d
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;