net: ethtool: make dev->hwprov ops-protected

dev->hwprov tracks the active hwtstamp provider for the device.
Make it ops protected (instance lock if the netdev driver opts
into holding instance lock around callbacks, otherwise rtnl_lock).

hwprov is written and read in:
 - drivers/net/phy/phy_device.c
    phydev and ops protection don't currently mix, add a comment
 - net/ethtool/
    as of now holds both rtnl lock and ops lock, this one will
    soon only hold one lock or the other

read in:
 - net/core/dev_ioctl.c
    holds both rtnl lock and ops lock
 - net/core/timestamping.c
    RCU reader

The new netdev_ops_lock_dereference() helper does not have
"compat" in the name. The name would be quite long and I think
in this case it should be obvious that we need _a_ lock.
netdev_lock_dereference() already exists and means dev->lock
is always expected.

Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20260605002912.3456868-4-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 3370eb822017b264cfc26881b0eade8a49e1530f..ea53e477465d764f45e6906cac5151208c0e8af2 100644 (file)
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1935,6 +1935,9 @@ void phy_detach(struct phy_device *phydev)
        if (dev) {
                struct hwtstamp_provider *hwprov;
 
+               /* hwprov may technically be protected by ops lock but
+                * not for devices with a phydev, see phy_link_topo_add_phy()
+                */
                hwprov = rtnl_dereference(dev->hwprov);
                /* Disable timestamp if it is the one selected */
                if (hwprov && hwprov->phydev == phydev) {

diff --git a/drivers/net/phy/phy_link_topology.c b/drivers/net/phy/phy_link_topology.c
index aed3b26c1674f04abcefe87ec3d0cddd982edae0..4134de7ae313d2a086fca1c2fd7a9bb02bf5cf3d 100644 (file)
--- a/drivers/net/phy/phy_link_topology.c
+++ b/drivers/net/phy/phy_link_topology.c
@@ -38,7 +38,9 @@ int phy_link_topo_add_phy(struct net_device *dev,
 
        /* ethtool ops may run without rtnl_lock, and rtnl_lock is what
         * currently protects the PHY topology. No driver currently mixes
-        * the two, flag if someone tries. See also ethnl_req_get_phydev().
+        * the two, flag if someone tries. See also:
+        *  - ethnl_req_get_phydev()
+        *  - phy_detach()
         */
        if (WARN_ON_ONCE(netdev_need_ops_lock(dev)))
                return -EOPNOTSUPP;

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 74507c006490f180d2fac6594f6dcf2c86d53919..a8709d0cc8d476cac6c74397c0ebc751032ab508 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2583,6 +2583,9 @@ struct net_device {
         * Double protects:
         *      @up, @moving_ns, @nd_net, @xdp_features
         *
+        * Ops protects:
+        *      @hwprov
+        *
         * Double ops protects:
         *      @real_num_rx_queues, @real_num_tx_queues
         *

diff --git a/include/net/netdev_lock.h b/include/net/netdev_lock.h
index d3daec4e93f33d3cb8a43a48b0d3c50ae6c2a414..9fb3e93857c3d38e7a6910b58dc2d334695f2654 100644 (file)
--- a/include/net/netdev_lock.h
+++ b/include/net/netdev_lock.h
@@ -102,6 +102,14 @@ static inline void netdev_unlock_ops_compat(struct net_device *dev)
                rtnl_unlock();
 }
 
+/* Matching "ops protected" category from netdevice.h */
+static inline int netdev_is_locked_ops_compat(const struct net_device *dev)
+{
+       if (netdev_need_ops_lock(dev))
+               return lockdep_is_held(&dev->lock);
+       return lockdep_rtnl_is_held();
+}
+
 static inline int netdev_lock_cmp_fn(const struct lockdep_map *a,
                                     const struct lockdep_map *b)
 {
@@ -138,6 +146,9 @@ static inline int netdev_lock_cmp_fn(const struct lockdep_map *a,
 #define netdev_lock_dereference(p, dev)                                \
        rcu_dereference_protected(p, lockdep_is_held(&(dev)->lock))
 
+#define netdev_ops_lock_dereference(p, dev)                            \
+       rcu_dereference_protected(p, netdev_is_locked_ops_compat(dev))
+
 int netdev_debug_event(struct notifier_block *nb, unsigned long event,
                       void *ptr);
 

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index f3979b276090c63a52c94855e9f73cacee73450a..a320e264eaaf0961eaac67e82f377d62f54773c0 100644 (file)
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -260,7 +260,7 @@ int dev_get_hwtstamp_phylib(struct net_device *dev,
 {
        struct hwtstamp_provider *hwprov;
 
-       hwprov = rtnl_dereference(dev->hwprov);
+       hwprov = netdev_ops_lock_dereference(dev->hwprov, dev);
        if (hwprov) {
                cfg->qualifier = hwprov->desc.qualifier;
                if (hwprov->source == HWTSTAMP_SOURCE_PHYLIB &&
@@ -337,7 +337,7 @@ int dev_set_hwtstamp_phylib(struct net_device *dev,
        bool phy_ts;
        int err;
 
-       hwprov = rtnl_dereference(dev->hwprov);
+       hwprov = netdev_ops_lock_dereference(dev->hwprov, dev);
        if (hwprov) {
                if (hwprov->source == HWTSTAMP_SOURCE_PHYLIB &&
                    hwprov->phydev) {

diff --git a/net/ethtool/tsconfig.c b/net/ethtool/tsconfig.c
index 664c3fe49b5bebec6addb05b225d91d8bb759d1d..24b64862011f0b231ecf592aa832bd2fa431f968 100644 (file)
--- a/net/ethtool/tsconfig.c
+++ b/net/ethtool/tsconfig.c
@@ -2,6 +2,7 @@
 
 #include <linux/net_tstamp.h>
 #include <linux/ptp_clock_kernel.h>
+#include <net/netdev_lock.h>
 
 #include "bitset.h"
 #include "common.h"
@@ -57,7 +58,7 @@ static int tsconfig_prepare_data(const struct ethnl_req_info *req_base,
        data->hwtst_config.flags = cfg.flags;
 
        data->hwprov_desc.index = -1;
-       hwprov = rtnl_dereference(dev->hwprov);
+       hwprov = netdev_ops_lock_dereference(dev->hwprov, dev);
        if (hwprov) {
                data->hwprov_desc.index = hwprov->desc.index;
                data->hwprov_desc.qualifier = hwprov->desc.qualifier;
@@ -213,7 +214,7 @@ static int tsconfig_send_reply(struct net_device *dev, struct genl_info *info)
                return -ENOMEM;
        }
 
-       ASSERT_RTNL();
+       netdev_assert_locked_ops_compat(dev);
        reply_data->base.dev = dev;
        ret = tsconfig_prepare_data(&req_info->base, &reply_data->base, info);
        if (ret < 0)
@@ -316,7 +317,7 @@ static int ethnl_set_tsconfig(struct ethnl_req_info *req_base,
                struct hwtstamp_provider_desc __hwprov_desc = {.index = -1};
                struct hwtstamp_provider *__hwprov;
 
-               __hwprov = rtnl_dereference(dev->hwprov);
+               __hwprov = netdev_ops_lock_dereference(dev->hwprov, dev);
                if (__hwprov) {
                        __hwprov_desc.index = __hwprov->desc.index;
                        __hwprov_desc.qualifier = __hwprov->desc.qualifier;
@@ -414,7 +415,8 @@ static int ethnl_set_tsconfig(struct ethnl_req_info *req_base,
                        goto err_free_hwprov;
 
                /* Change the selected hwtstamp source */
-               __hwprov = rcu_replace_pointer_rtnl(dev->hwprov, hwprov);
+               __hwprov = rcu_replace_pointer(dev->hwprov, hwprov,
+                                              netdev_is_locked_ops_compat(dev));
                if (__hwprov)
                        kfree_rcu(__hwprov, rcu_head);
        }