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charset="UTF-8" From: Pin-yen Lin Fix a concurrency bug where network statistics queries race with queue reconfiguration or interface teardown, causing a Use-After-Free (UAF) or NULL pointer dereference. Currently, statistics queries access priv->tx and priv->rx without locking. When an interface is brought down or reconfigured, gve_queues_mem_remove() frees these arrays. A concurrent stats query can dereference freed queue structures and crash the kernel. This issue was discovered and actually triggered by the drivers/net/stats.py selftest. When an interface was brought down, querying per-queue statistics via Netlink caused a kernel NULL pointer dereference in gve_get_rx_queue_stats(): BUG: kernel NULL pointer dereference, address: 00000000000000a0 RIP: 0010:gve_get_rx_queue_stats+0x17/0x50 [gve] Call Trace: netdev_stat_queue_sum+0x11c/0x250 netdev_nl_stats_by_netdev+0x21b/0x2d0 netdev_nl_qstats_get_dumpit+0xd2/0x220 genl_dumpit+0x32/0x90 netlink_dump+0x1d2/0x450 __netlink_dump_start+0x1db/0x2a0 genl_family_rcv_msg_dumpit+0x9b/0x100 ... The per-queue stats callbacks run under the netdev instance lock, so this NULL dereference is not a race; it happens on any query while the interface is down. Additionally, concurrent stats queries during queue reconfiguration can race with gve_queues_mem_remove(), causing a Use-After-Free. This affects gve_get_stats() and gve_handle_report_stats(), which do not hold the instance lock. Fix this by introducing stats_lock to serialize stats queries against queue teardown. In gve_queues_mem_remove(), queue pointers are set to NULL under stats_lock before freeing. Stats readers acquire the lock and verify pointers are non-NULL before reading counters. The per-queue stats callbacks also take stats_lock so that all readers follow the same locking rule. This change was tested using the DQO RDA queue format. Cc: stable@vger.kernel.org Fixes: f5cedc84a30d ("gve: Add transmit and receive support") Co-developed-by: Debarghya Kundu Signed-off-by: Debarghya Kundu Signed-off-by: Pin-yen Lin Signed-off-by: Harshitha Ramamurthy --- Changes in v4: - Clarify in the commit message that the qstats NULL dereference is not a race, and which readers race with queue teardown (Sashiko) - Change the Fixes tag to f5cedc84a30d (Sashiko) Changes in v3: - Retitled from "gve: Add NULL pointer checks for per-queue statistics" - Protect all stats queries and queue lifecycle updates with spinlock (sashiko) - Refined the commit message drivers/net/ethernet/google/gve/gve.h | 2 ++ drivers/net/ethernet/google/gve/gve_main.c | 37 +++++++++++++++++++--- 2 files changed, 35 insertions(+), 4 deletions(-) diff --git a/drivers/net/ethernet/google/gve/gve.h b/drivers/net/ethernet/google/gve/gve.h index b7ce6e8632db..104468c2c07f 100644 --- a/drivers/net/ethernet/google/gve/gve.h +++ b/drivers/net/ethernet/google/gve/gve.h @@ -957,6 +957,8 @@ struct gve_priv { struct workqueue_struct *gve_wq; struct work_struct service_task; struct work_struct stats_report_task; + /* Synchronizes stats accesses and queue teardown */ + spinlock_t stats_lock; unsigned long service_task_flags; unsigned long state_flags; diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c index 2437cd8ba633..26fdd22644f4 100644 --- a/drivers/net/ethernet/google/gve/gve_main.c +++ b/drivers/net/ethernet/google/gve/gve_main.c @@ -69,6 +69,7 @@ static void gve_get_stats(struct net_device *dev, struct rtnl_link_stats64 *s) int num_tx_queues; int ring; + spin_lock_bh(&priv->stats_lock); num_tx_queues = gve_num_tx_queues(priv); if (priv->rx) { for (ring = 0; ring < priv->rx_cfg.num_queues; ring++) { @@ -96,6 +97,7 @@ static void gve_get_stats(struct net_device *dev, struct rtnl_link_stats64 *s) s->tx_bytes += bytes; } } + spin_unlock_bh(&priv->stats_lock); } static int gve_alloc_flow_rule_caches(struct gve_priv *priv) @@ -642,9 +644,13 @@ static void gve_queues_mem_remove(struct gve_priv *priv) struct gve_rx_alloc_rings_cfg rx_alloc_cfg = {0}; gve_get_curr_alloc_cfgs(priv, &tx_alloc_cfg, &rx_alloc_cfg); - gve_queues_mem_free(priv, &tx_alloc_cfg, &rx_alloc_cfg); + + spin_lock_bh(&priv->stats_lock); priv->tx = NULL; priv->rx = NULL; + spin_unlock_bh(&priv->stats_lock); + + gve_queues_mem_free(priv, &tx_alloc_cfg, &rx_alloc_cfg); } static void gve_free_control_plane_resources(struct gve_priv *priv) @@ -1383,6 +1389,7 @@ static int gve_queues_start(struct gve_priv *priv, int err; /* Record new resources into priv */ + spin_lock_bh(&priv->stats_lock); priv->tx = tx_alloc_cfg->tx; priv->rx = rx_alloc_cfg->rx; @@ -1396,10 +1403,11 @@ static int gve_queues_start(struct gve_priv *priv, priv->rx_pages_per_qpl = rx_alloc_cfg->pages_per_qpl; priv->header_split_enabled = rx_alloc_cfg->enable_header_split; priv->rx_cfg.packet_buffer_size = rx_alloc_cfg->packet_buffer_size; + gve_init_sync_stats(priv); + spin_unlock_bh(&priv->stats_lock); gve_tx_start_rings(priv, gve_num_tx_queues(priv)); gve_rx_start_rings(priv, rx_alloc_cfg->qcfg_rx->num_queues); - gve_init_sync_stats(priv); err = netif_set_real_num_tx_queues(dev, priv->tx_cfg.num_queues); if (err) @@ -2266,6 +2274,7 @@ void gve_handle_report_stats(struct gve_priv *priv) if (!gve_get_report_stats(priv)) return; + spin_lock_bh(&priv->stats_lock); be64_add_cpu(&priv->stats_report->written_count, 1); /* tx stats */ if (priv->tx) { @@ -2330,6 +2339,7 @@ void gve_handle_report_stats(struct gve_priv *priv) }; } } + spin_unlock_bh(&priv->stats_lock); } /* Handle NIC status register changes, reset requests and report stats */ @@ -2786,9 +2796,15 @@ static void gve_get_rx_queue_stats(struct net_device *dev, int idx, struct netdev_queue_stats_rx *rx_stats) { struct gve_priv *priv = netdev_priv(dev); - struct gve_rx_ring *rx = &priv->rx[idx]; + struct gve_rx_ring *rx; unsigned int start; + spin_lock_bh(&priv->stats_lock); + if (!priv->rx) + goto unlock; + + rx = &priv->rx[idx]; + do { start = u64_stats_fetch_begin(&rx->statss); rx_stats->packets = rx->rpackets; @@ -2796,20 +2812,32 @@ static void gve_get_rx_queue_stats(struct net_device *dev, int idx, rx_stats->alloc_fail = rx->rx_skb_alloc_fail + rx->rx_buf_alloc_fail; } while (u64_stats_fetch_retry(&rx->statss, start)); + +unlock: + spin_unlock_bh(&priv->stats_lock); } static void gve_get_tx_queue_stats(struct net_device *dev, int idx, struct netdev_queue_stats_tx *tx_stats) { struct gve_priv *priv = netdev_priv(dev); - struct gve_tx_ring *tx = &priv->tx[idx]; + struct gve_tx_ring *tx; unsigned int start; + spin_lock_bh(&priv->stats_lock); + if (!priv->tx) + goto unlock; + + tx = &priv->tx[idx]; + do { start = u64_stats_fetch_begin(&tx->statss); tx_stats->packets = tx->pkt_done; tx_stats->bytes = tx->bytes_done; } while (u64_stats_fetch_retry(&tx->statss, start)); + +unlock: + spin_unlock_bh(&priv->stats_lock); } static void gve_get_base_stats(struct net_device *dev, @@ -2935,6 +2963,7 @@ static int gve_probe(struct pci_dev *pdev, const struct pci_device_id *ent) } INIT_WORK(&priv->service_task, gve_service_task); INIT_WORK(&priv->stats_report_task, gve_stats_report_task); + spin_lock_init(&priv->stats_lock); priv->tx_cfg.max_queues = max_tx_queues; priv->rx_cfg.max_queues = max_rx_queues; -- 2.56.0.313.g2479322e68-goog