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    Subject[PATCH 3.18 12/45] tg3: Fix vunmap() BUG_ON() triggered from tg3_free_consistent().
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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
    @@ -8705,14 +8705,15 @@ 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);
    }

    /*
    @@ -14137,7 +14138,7 @@ static struct rtnl_link_stats64 *tg3_get
    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 stats;

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