From: Sukadev Bhattiprolu sukadev@linux.ibm.com
[ Upstream commit 4219196d1f662cb10a462eb9e076633a3fc31a15 ]
There is a race between reset and the transmit paths that can lead to ibmvnic_xmit() accessing an scrq after it has been freed in the reset path. It can result in a crash like:
Kernel attempted to read user page (0) - exploit attempt? (uid: 0) BUG: Kernel NULL pointer dereference on read at 0x00000000 Faulting instruction address: 0xc0080000016189f8 Oops: Kernel access of bad area, sig: 11 [#1] ... NIP [c0080000016189f8] ibmvnic_xmit+0x60/0xb60 [ibmvnic] LR [c000000000c0046c] dev_hard_start_xmit+0x11c/0x280 Call Trace: [c008000001618f08] ibmvnic_xmit+0x570/0xb60 [ibmvnic] (unreliable) [c000000000c0046c] dev_hard_start_xmit+0x11c/0x280 [c000000000c9cfcc] sch_direct_xmit+0xec/0x330 [c000000000bfe640] __dev_xmit_skb+0x3a0/0x9d0 [c000000000c00ad4] __dev_queue_xmit+0x394/0x730 [c008000002db813c] __bond_start_xmit+0x254/0x450 [bonding] [c008000002db8378] bond_start_xmit+0x40/0xc0 [bonding] [c000000000c0046c] dev_hard_start_xmit+0x11c/0x280 [c000000000c00ca4] __dev_queue_xmit+0x564/0x730 [c000000000cf97e0] neigh_hh_output+0xd0/0x180 [c000000000cfa69c] ip_finish_output2+0x31c/0x5c0 [c000000000cfd244] __ip_queue_xmit+0x194/0x4f0 [c000000000d2a3c4] __tcp_transmit_skb+0x434/0x9b0 [c000000000d2d1e0] __tcp_retransmit_skb+0x1d0/0x6a0 [c000000000d2d984] tcp_retransmit_skb+0x34/0x130 [c000000000d310e8] tcp_retransmit_timer+0x388/0x6d0 [c000000000d315ec] tcp_write_timer_handler+0x1bc/0x330 [c000000000d317bc] tcp_write_timer+0x5c/0x200 [c000000000243270] call_timer_fn+0x50/0x1c0 [c000000000243704] __run_timers.part.0+0x324/0x460 [c000000000243894] run_timer_softirq+0x54/0xa0 [c000000000ea713c] __do_softirq+0x15c/0x3e0 [c000000000166258] __irq_exit_rcu+0x158/0x190 [c000000000166420] irq_exit+0x20/0x40 [c00000000002853c] timer_interrupt+0x14c/0x2b0 [c000000000009a00] decrementer_common_virt+0x210/0x220 --- interrupt: 900 at plpar_hcall_norets_notrace+0x18/0x2c
The immediate cause of the crash is the access of tx_scrq in the following snippet during a reset, where the tx_scrq can be either NULL or an address that will soon be invalid:
ibmvnic_xmit() { ... tx_scrq = adapter->tx_scrq[queue_num]; txq = netdev_get_tx_queue(netdev, queue_num); ind_bufp = &tx_scrq->ind_buf;
if (test_bit(0, &adapter->resetting)) { ... }
But beyond that, the call to ibmvnic_xmit() itself is not safe during a reset and the reset path attempts to avoid this by stopping the queue in ibmvnic_cleanup(). However just after the queue was stopped, an in-flight ibmvnic_complete_tx() could have restarted the queue even as the reset is progressing.
Since the queue was restarted we could get a call to ibmvnic_xmit() which can then access the bad tx_scrq (or other fields).
We cannot however simply have ibmvnic_complete_tx() check the ->resetting bit and skip starting the queue. This can race at the "back-end" of a good reset which just restarted the queue but has not cleared the ->resetting bit yet. If we skip restarting the queue due to ->resetting being true, the queue would remain stopped indefinitely potentially leading to transmit timeouts.
IOW ->resetting is too broad for this purpose. Instead use a new flag that indicates whether or not the queues are active. Only the open/ reset paths control when the queues are active. ibmvnic_complete_tx() and others wake up the queue only if the queue is marked active.
So we will have: A. reset/open thread in ibmvnic_cleanup() and __ibmvnic_open()
->resetting = true ->tx_queues_active = false disable tx queues ... ->tx_queues_active = true start tx queues
B. Tx interrupt in ibmvnic_complete_tx():
if (->tx_queues_active) netif_wake_subqueue();
To ensure that ->tx_queues_active and state of the queues are consistent, we need a lock which:
- must also be taken in the interrupt path (ibmvnic_complete_tx()) - shared across the multiple queues in the adapter (so they don't become serialized)
Use rcu_read_lock() and have the reset thread synchronize_rcu() after updating the ->tx_queues_active state.
While here, consolidate a few boolean fields in ibmvnic_adapter for better alignment.
Based on discussions with Brian King and Dany Madden.
Fixes: 7ed5b31f4a66 ("net/ibmvnic: prevent more than one thread from running in reset") Reported-by: Vaishnavi Bhat vaish123@in.ibm.com Signed-off-by: Sukadev Bhattiprolu sukadev@linux.ibm.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/ibm/ibmvnic.c | 63 ++++++++++++++++++++++++------ drivers/net/ethernet/ibm/ibmvnic.h | 7 +++- 2 files changed, 55 insertions(+), 15 deletions(-)
diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c index b423e94956f1..b4804ce63151 100644 --- a/drivers/net/ethernet/ibm/ibmvnic.c +++ b/drivers/net/ethernet/ibm/ibmvnic.c @@ -1429,6 +1429,15 @@ static int __ibmvnic_open(struct net_device *netdev) return rc; }
+ adapter->tx_queues_active = true; + + /* Since queues were stopped until now, there shouldn't be any + * one in ibmvnic_complete_tx() or ibmvnic_xmit() so maybe we + * don't need the synchronize_rcu()? Leaving it for consistency + * with setting ->tx_queues_active = false. + */ + synchronize_rcu(); + netif_tx_start_all_queues(netdev);
if (prev_state == VNIC_CLOSED) { @@ -1603,6 +1612,14 @@ static void ibmvnic_cleanup(struct net_device *netdev) struct ibmvnic_adapter *adapter = netdev_priv(netdev);
/* ensure that transmissions are stopped if called by do_reset */ + + adapter->tx_queues_active = false; + + /* Ensure complete_tx() and ibmvnic_xmit() see ->tx_queues_active + * update so they don't restart a queue after we stop it below. + */ + synchronize_rcu(); + if (test_bit(0, &adapter->resetting)) netif_tx_disable(netdev); else @@ -1842,14 +1859,21 @@ static void ibmvnic_tx_scrq_clean_buffer(struct ibmvnic_adapter *adapter, tx_buff->skb = NULL; adapter->netdev->stats.tx_dropped++; } + ind_bufp->index = 0; + if (atomic_sub_return(entries, &tx_scrq->used) <= (adapter->req_tx_entries_per_subcrq / 2) && - __netif_subqueue_stopped(adapter->netdev, queue_num) && - !test_bit(0, &adapter->resetting)) { - netif_wake_subqueue(adapter->netdev, queue_num); - netdev_dbg(adapter->netdev, "Started queue %d\n", - queue_num); + __netif_subqueue_stopped(adapter->netdev, queue_num)) { + rcu_read_lock(); + + if (adapter->tx_queues_active) { + netif_wake_subqueue(adapter->netdev, queue_num); + netdev_dbg(adapter->netdev, "Started queue %d\n", + queue_num); + } + + rcu_read_unlock(); } }
@@ -1904,11 +1928,12 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev) int index = 0; u8 proto = 0;
- tx_scrq = adapter->tx_scrq[queue_num]; - txq = netdev_get_tx_queue(netdev, queue_num); - ind_bufp = &tx_scrq->ind_buf; - - if (test_bit(0, &adapter->resetting)) { + /* If a reset is in progress, drop the packet since + * the scrqs may get torn down. Otherwise use the + * rcu to ensure reset waits for us to complete. + */ + rcu_read_lock(); + if (!adapter->tx_queues_active) { dev_kfree_skb_any(skb);
tx_send_failed++; @@ -1917,6 +1942,10 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev) goto out; }
+ tx_scrq = adapter->tx_scrq[queue_num]; + txq = netdev_get_tx_queue(netdev, queue_num); + ind_bufp = &tx_scrq->ind_buf; + if (ibmvnic_xmit_workarounds(skb, netdev)) { tx_dropped++; tx_send_failed++; @@ -1924,6 +1953,7 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev) ibmvnic_tx_scrq_flush(adapter, tx_scrq); goto out; } + if (skb_is_gso(skb)) tx_pool = &adapter->tso_pool[queue_num]; else @@ -2078,6 +2108,7 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev) netif_carrier_off(netdev); } out: + rcu_read_unlock(); netdev->stats.tx_dropped += tx_dropped; netdev->stats.tx_bytes += tx_bytes; netdev->stats.tx_packets += tx_packets; @@ -3732,9 +3763,15 @@ static int ibmvnic_complete_tx(struct ibmvnic_adapter *adapter, (adapter->req_tx_entries_per_subcrq / 2) && __netif_subqueue_stopped(adapter->netdev, scrq->pool_index)) { - netif_wake_subqueue(adapter->netdev, scrq->pool_index); - netdev_dbg(adapter->netdev, "Started queue %d\n", - scrq->pool_index); + rcu_read_lock(); + if (adapter->tx_queues_active) { + netif_wake_subqueue(adapter->netdev, + scrq->pool_index); + netdev_dbg(adapter->netdev, + "Started queue %d\n", + scrq->pool_index); + } + rcu_read_unlock(); } }
diff --git a/drivers/net/ethernet/ibm/ibmvnic.h b/drivers/net/ethernet/ibm/ibmvnic.h index fa2d607a7b1b..8f5cefb932dd 100644 --- a/drivers/net/ethernet/ibm/ibmvnic.h +++ b/drivers/net/ethernet/ibm/ibmvnic.h @@ -1006,11 +1006,14 @@ struct ibmvnic_adapter { struct work_struct ibmvnic_reset; struct delayed_work ibmvnic_delayed_reset; unsigned long resetting; - bool napi_enabled, from_passive_init; - bool login_pending; /* last device reset time */ unsigned long last_reset_time;
+ bool napi_enabled; + bool from_passive_init; + bool login_pending; + /* protected by rcu */ + bool tx_queues_active; bool failover_pending; bool force_reset_recovery;