From 1a51502bddca7ac1e921d918b741ffd2bec149ed Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 16 Nov 2010 19:26:42 -0800 Subject: [PATCH] ixgbe: delay rx_ring freeing "cat /proc/net/dev" uses RCU protection only. Its quite possible we call a driver get_stats() method while device is dismantling and freeing its data structures. So get_stats() methods must be very careful not accessing driver private data without appropriate locking. In ixgbe case, we access rx_ring pointers. These pointers are freed in ixgbe_clear_interrupt_scheme() and set to NULL, this can trigger NULL dereference in ixgbe_get_stats64() A possible fix is to use RCU locking in ixgbe_get_stats64() and defer rx_ring freeing after a grace period in ixgbe_clear_interrupt_scheme() Signed-off-by: Eric Dumazet Reported-by: Tantilov, Emil S Tested-by: Ross Brattain Signed-off-by: Jeff Kirsher --- drivers/net/ixgbe/ixgbe.h | 1 + drivers/net/ixgbe/ixgbe_main.c | 34 ++++++++++++++++++++++++---------- 2 files changed, 25 insertions(+), 10 deletions(-) diff --git a/drivers/net/ixgbe/ixgbe.h b/drivers/net/ixgbe/ixgbe.h index ed8703cfffb7..018e143612b2 100644 --- a/drivers/net/ixgbe/ixgbe.h +++ b/drivers/net/ixgbe/ixgbe.h @@ -192,6 +192,7 @@ struct ixgbe_ring { unsigned int size; /* length in bytes */ dma_addr_t dma; /* phys. address of descriptor ring */ + struct rcu_head rcu; } ____cacheline_internodealigned_in_smp; enum ixgbe_ring_f_enum { diff --git a/drivers/net/ixgbe/ixgbe_main.c b/drivers/net/ixgbe/ixgbe_main.c index fbad4d819608..a137f9dbaacd 100644 --- a/drivers/net/ixgbe/ixgbe_main.c +++ b/drivers/net/ixgbe/ixgbe_main.c @@ -4751,6 +4751,11 @@ err_set_interrupt: return err; } +static void ring_free_rcu(struct rcu_head *head) +{ + kfree(container_of(head, struct ixgbe_ring, rcu)); +} + /** * ixgbe_clear_interrupt_scheme - Clear the current interrupt scheme settings * @adapter: board private structure to clear interrupt scheme on @@ -4767,7 +4772,12 @@ void ixgbe_clear_interrupt_scheme(struct ixgbe_adapter *adapter) adapter->tx_ring[i] = NULL; } for (i = 0; i < adapter->num_rx_queues; i++) { - kfree(adapter->rx_ring[i]); + struct ixgbe_ring *ring = adapter->rx_ring[i]; + + /* ixgbe_get_stats64() might access this ring, we must wait + * a grace period before freeing it. + */ + call_rcu(&ring->rcu, ring_free_rcu); adapter->rx_ring[i] = NULL; } @@ -6563,20 +6573,23 @@ static struct rtnl_link_stats64 *ixgbe_get_stats64(struct net_device *netdev, /* accurate rx/tx bytes/packets stats */ dev_txq_stats_fold(netdev, stats); + rcu_read_lock(); for (i = 0; i < adapter->num_rx_queues; i++) { - struct ixgbe_ring *ring = adapter->rx_ring[i]; + struct ixgbe_ring *ring = ACCESS_ONCE(adapter->rx_ring[i]); u64 bytes, packets; unsigned int start; - do { - start = u64_stats_fetch_begin_bh(&ring->syncp); - packets = ring->stats.packets; - bytes = ring->stats.bytes; - } while (u64_stats_fetch_retry_bh(&ring->syncp, start)); - stats->rx_packets += packets; - stats->rx_bytes += bytes; + if (ring) { + do { + start = u64_stats_fetch_begin_bh(&ring->syncp); + packets = ring->stats.packets; + bytes = ring->stats.bytes; + } while (u64_stats_fetch_retry_bh(&ring->syncp, start)); + stats->rx_packets += packets; + stats->rx_bytes += bytes; + } } - + rcu_read_unlock(); /* following stats updated by ixgbe_watchdog_task() */ stats->multicast = netdev->stats.multicast; stats->rx_errors = netdev->stats.rx_errors; @@ -7282,6 +7295,7 @@ static void __exit ixgbe_exit_module(void) dca_unregister_notify(&dca_notifier); #endif pci_unregister_driver(&ixgbe_driver); + rcu_barrier(); /* Wait for completion of call_rcu()'s */ } #ifdef CONFIG_IXGBE_DCA -- 2.20.1