sfc: protect filter table against use-after-free

If MCDI timeouts are encountered during efx_ef10_filter_table_remove(),
an FLR will be queued, but efx->filter_state will still be kfree()d.
The queued FLR will then call efx_ef10_filter_table_restore(), which
will try to use efx->filter_state. This previously caused a panic.
This patch adds an rwsem to protect the existence of efx->filter_state,
separately from the spinlock protecting its contents.  Users which can
race against efx_ef10_filter_table_remove() should down_read this rwsem.

Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/sfc/ef10.c b/drivers/net/ethernet/sfc/ef10.c
index 78d3236..9e2e8e1 100644 (file)
--- a/drivers/net/ethernet/sfc/ef10.c
+++ b/drivers/net/ethernet/sfc/ef10.c
@@ -3314,6 +3314,9 @@ fail:
        return rc;
 }
 
+/* Caller must hold efx->filter_sem for read if race against
+ * efx_ef10_filter_table_remove() is possible
+ */
 static void efx_ef10_filter_table_restore(struct efx_nic *efx)
 {
        struct efx_ef10_filter_table *table = efx->filter_state;
@@ -3323,9 +3326,14 @@ static void efx_ef10_filter_table_restore(struct efx_nic *efx)
        bool failed = false;
        int rc;
 
+       WARN_ON(!rwsem_is_locked(&efx->filter_sem));
+
        if (!nic_data->must_restore_filters)
                return;
 
+       if (!table)
+               return;
+
        spin_lock_bh(&efx->filter_lock);
 
        for (filter_idx = 0; filter_idx < HUNT_FILTER_TBL_ROWS; filter_idx++) {
@@ -3361,6 +3369,7 @@ static void efx_ef10_filter_table_restore(struct efx_nic *efx)
                nic_data->must_restore_filters = false;
 }
 
+/* Caller must hold efx->filter_sem for write */
 static void efx_ef10_filter_table_remove(struct efx_nic *efx)
 {
        struct efx_ef10_filter_table *table = efx->filter_state;
@@ -3369,6 +3378,10 @@ static void efx_ef10_filter_table_remove(struct efx_nic *efx)
        unsigned int filter_idx;
        int rc;
 
+       efx->filter_state = NULL;
+       if (!table)
+               return;
+
        for (filter_idx = 0; filter_idx < HUNT_FILTER_TBL_ROWS; filter_idx++) {
                spec = efx_ef10_filter_entry_spec(table, filter_idx);
                if (!spec)
@@ -3394,6 +3407,9 @@ static void efx_ef10_filter_table_remove(struct efx_nic *efx)
        kfree(table);
 }
 
+/* Caller must hold efx->filter_sem for read if race against
+ * efx_ef10_filter_table_remove() is possible
+ */
 static void efx_ef10_filter_sync_rx_mode(struct efx_nic *efx)
 {
        struct efx_ef10_filter_table *table = efx->filter_state;
@@ -3408,6 +3424,9 @@ static void efx_ef10_filter_sync_rx_mode(struct efx_nic *efx)
        if (!efx_dev_registered(efx))
                return;
 
+       if (!table)
+               return;
+
        /* Mark old filters that may need to be removed */
        spin_lock_bh(&efx->filter_lock);
        n = table->dev_uc_count < 0 ? 1 : table->dev_uc_count;

diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 864c337..50816cd 100644 (file)
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -949,6 +949,16 @@ void efx_link_set_wanted_fc(struct efx_nic *efx, u8 wanted_fc)
 
 static void efx_fini_port(struct efx_nic *efx);
 
+/* We assume that efx->type->reconfigure_mac will always try to sync RX
+ * filters and therefore needs to read-lock the filter table against freeing
+ */
+void efx_mac_reconfigure(struct efx_nic *efx)
+{
+       down_read(&efx->filter_sem);
+       efx->type->reconfigure_mac(efx);
+       up_read(&efx->filter_sem);
+}
+
 /* Push loopback/power/transmit disable settings to the PHY, and reconfigure
  * the MAC appropriately. All other PHY configuration changes are pushed
  * through phy_op->set_settings(), and pushed asynchronously to the MAC
@@ -1002,7 +1012,7 @@ static void efx_mac_work(struct work_struct *data)
 
        mutex_lock(&efx->mac_lock);
        if (efx->port_enabled)
-               efx->type->reconfigure_mac(efx);
+               efx_mac_reconfigure(efx);
        mutex_unlock(&efx->mac_lock);
 }
 
@@ -1042,7 +1052,7 @@ static int efx_init_port(struct efx_nic *efx)
 
        /* Reconfigure the MAC before creating dma queues (required for
         * Falcon/A1 where RX_INGR_EN/TX_DRAIN_EN isn't supported) */
-       efx->type->reconfigure_mac(efx);
+       efx_mac_reconfigure(efx);
 
        /* Ensure the PHY advertises the correct flow control settings */
        rc = efx->phy_op->reconfigure(efx);
@@ -1068,7 +1078,7 @@ static void efx_start_port(struct efx_nic *efx)
        efx->port_enabled = true;
 
        /* Ensure MAC ingress/egress is enabled */
-       efx->type->reconfigure_mac(efx);
+       efx_mac_reconfigure(efx);
 
        mutex_unlock(&efx->mac_lock);
 }
@@ -1672,10 +1682,11 @@ static int efx_probe_filters(struct efx_nic *efx)
        int rc;
 
        spin_lock_init(&efx->filter_lock);
-
+       init_rwsem(&efx->filter_sem);
+       down_write(&efx->filter_sem);
        rc = efx->type->filter_table_probe(efx);
        if (rc)
-               return rc;
+               goto out_unlock;
 
 #ifdef CONFIG_RFS_ACCEL
        if (efx->type->offload_features & NETIF_F_NTUPLE) {
@@ -1684,12 +1695,14 @@ static int efx_probe_filters(struct efx_nic *efx)
                                           GFP_KERNEL);
                if (!efx->rps_flow_id) {
                        efx->type->filter_table_remove(efx);
-                       return -ENOMEM;
+                       rc = -ENOMEM;
+                       goto out_unlock;
                }
        }
 #endif
-
-       return 0;
+out_unlock:
+       up_write(&efx->filter_sem);
+       return rc;
 }
 
 static void efx_remove_filters(struct efx_nic *efx)
@@ -1697,12 +1710,16 @@ static void efx_remove_filters(struct efx_nic *efx)
 #ifdef CONFIG_RFS_ACCEL
        kfree(efx->rps_flow_id);
 #endif
+       down_write(&efx->filter_sem);
        efx->type->filter_table_remove(efx);
+       up_write(&efx->filter_sem);
 }
 
 static void efx_restore_filters(struct efx_nic *efx)
 {
+       down_read(&efx->filter_sem);
        efx->type->filter_table_restore(efx);
+       up_read(&efx->filter_sem);
 }
 
 /**************************************************************************
@@ -2183,7 +2200,7 @@ static int efx_change_mtu(struct net_device *net_dev, int new_mtu)
 
        mutex_lock(&efx->mac_lock);
        net_dev->mtu = new_mtu;
-       efx->type->reconfigure_mac(efx);
+       efx_mac_reconfigure(efx);
        mutex_unlock(&efx->mac_lock);
 
        efx_start_all(efx);
@@ -2219,7 +2236,7 @@ static int efx_set_mac_address(struct net_device *net_dev, void *data)
 
        /* Reconfigure the MAC */
        mutex_lock(&efx->mac_lock);
-       efx->type->reconfigure_mac(efx);
+       efx_mac_reconfigure(efx);
        mutex_unlock(&efx->mac_lock);
 
        return 0;
@@ -2464,7 +2481,9 @@ int efx_reset_up(struct efx_nic *efx, enum reset_type method, bool ok)
                           " VFs may not function\n", rc);
 #endif
 
+       down_read(&efx->filter_sem);
        efx_restore_filters(efx);
+       up_read(&efx->filter_sem);
        if (efx->type->sriov_reset)
                efx->type->sriov_reset(efx);
 

diff --git a/drivers/net/ethernet/sfc/efx.h b/drivers/net/ethernet/sfc/efx.h
index 9097906..46aee41 100644 (file)
--- a/drivers/net/ethernet/sfc/efx.h
+++ b/drivers/net/ethernet/sfc/efx.h
@@ -74,6 +74,8 @@ void efx_schedule_slow_fill(struct efx_rx_queue *rx_queue);
 
 /* Filters */
 
+void efx_mac_reconfigure(struct efx_nic *efx);
+
 /**
  * efx_filter_insert_filter - add or replace a filter
  * @efx: NIC in which to insert the filter

diff --git a/drivers/net/ethernet/sfc/ethtool.c b/drivers/net/ethernet/sfc/ethtool.c
index 03829b4..0347976 100644 (file)
--- a/drivers/net/ethernet/sfc/ethtool.c
+++ b/drivers/net/ethernet/sfc/ethtool.c
@@ -734,7 +734,7 @@ static int efx_ethtool_set_pauseparam(struct net_device *net_dev,
        /* Reconfigure the MAC. The PHY *may* generate a link state change event
         * if the user just changed the advertised capabilities, but there's no
         * harm doing this twice */
-       efx->type->reconfigure_mac(efx);
+       efx_mac_reconfigure(efx);
 
 out:
        mutex_unlock(&efx->mac_lock);

diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index 55a5f48..f6c4832 100644 (file)
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -25,6 +25,7 @@
 #include <linux/highmem.h>
 #include <linux/workqueue.h>
 #include <linux/mutex.h>
+#include <linux/rwsem.h>
 #include <linux/vmalloc.h>
 #include <linux/i2c.h>
 #include <linux/mtd/mtd.h>
@@ -896,7 +897,8 @@ struct vfdi_status;
  * @loopback_mode: Loopback status
  * @loopback_modes: Supported loopback mode bitmask
  * @loopback_selftest: Offline self-test private state
- * @filter_lock: Filter table lock
+ * @filter_sem: Filter table rw_semaphore, for freeing the table
+ * @filter_lock: Filter table lock, for mere content changes
  * @filter_state: Architecture-dependent filter table state
  * @rps_flow_id: Flow IDs of filters allocated for accelerated RFS,
  *     indexed by filter ID
@@ -1038,6 +1040,7 @@ struct efx_nic {
 
        void *loopback_selftest;
 
+       struct rw_semaphore filter_sem;
        spinlock_t filter_lock;
        void *filter_state;
 #ifdef CONFIG_RFS_ACCEL