[PATCH net-next] xdp: create locked/unlocked instances of xdp redirect target setters

Joshua Washington
2025-04-22T01:17:05Z

Commit 03df156dd3a6 ("xdp: double protect netdev->xdp_flags with
netdev->lock") introduces the netdev lock to xdp_set_features_flag().
The change includes a _locked version of the method, as it is possible
for a driver to have already acquired the netdev lock before calling
this helper. However, the same applies to
xdp_features_(set|clear)_redirect_flags(), which ends up calling the
unlocked version of xdp_set_features_flags() leading to deadlocks in
GVE, which grabs the netdev lock as part of its suspend, reset, and
shutdown processes:

[ 833.265543] WARNING: possible recursive locking detected
[ 833.270949] 6.15.0-rc1 #6 Tainted: G E
[ 833.276271] --------------------------------------------
[ 833.281681] systemd-shutdow/1 is trying to acquire lock:
[ 833.287090] ffff949d2b148c68 (&dev->lock){+.+.}-{4:4}, at: xdp_set_features_flag+0x29/0x90
[ 833.295470]
[ 833.295470] but task is already holding lock:
[ 833.301400] ffff949d2b148c68 (&dev->lock){+.+.}-{4:4}, at: gve_shutdown+0x44/0x90 [gve]
[ 833.309508]
[ 833.309508] other info that might help us debug this:
[ 833.316130] Possible unsafe locking scenario:
[ 833.316130]
[ 833.322142] CPU0
[ 833.324681] ----
[ 833.327220] lock(&dev->lock);
[ 833.330455] lock(&dev->lock);
[ 833.333689]
[ 833.333689] *** DEADLOCK ***
[ 833.333689]
[ 833.339701] May be due to missing lock nesting notation
[ 833.339701]
[ 833.346582] 5 locks held by systemd-shutdow/1:
[ 833.351205] #0: ffffffffa9c89130 (system_transition_mutex){+.+.}-{4:4}, at: __se_sys_reboot+0xe6/0x210
[ 833.360695] #1: ffff93b399e5c1b8 (&dev->mutex){....}-{4:4}, at: device_shutdown+0xb4/0x1f0
[ 833.369144] #2: ffff949d19a471b8 (&dev->mutex){....}-{4:4}, at: device_shutdown+0xc2/0x1f0
[ 833.377603] #3: ffffffffa9eca050 (rtnl_mutex){+.+.}-{4:4}, at: gve_shutdown+0x33/0x90 [gve]
[ 833.386138] #4: ffff949d2b148c68 (&dev->lock){+.+.}-{4:4}, at: gve_shutdown+0x44/0x90 [gve]

Introduce xdp_features_(set|clear)_redirect_target_locked() versions
which assume that the netdev lock has already been acquired before
setting the XDP feature flag and update GVE to use the locked version.

Cc: bpf@vger.kernel.org
Fixes: 03df156dd3a6 ("xdp: double protect netdev->xdp_flags with netdev->lock")
Tested-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Signed-off-by: Joshua Washington <joshwash@google.com>
---
drivers/net/ethernet/google/gve/gve_main.c | 4 ++--
include/net/xdp.h | 3 +++
net/core/xdp.c | 25 ++++++++++++++++++----
3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
index 8aaac9101377..446e4b6fd3f1 100644
--- a/drivers/net/ethernet/google/gve/gve_main.c
+++ b/drivers/net/ethernet/google/gve/gve_main.c
@@ -1830,7 +1830,7 @@ static void gve_turndown(struct gve_priv *priv)
/* Stop tx queues */
netif_tx_disable(priv->dev);

- xdp_features_clear_redirect_target(priv->dev);
+ xdp_features_clear_redirect_target_locked(priv->dev);

gve_clear_napi_enabled(priv);
gve_clear_report_stats(priv);
@@ -1902,7 +1902,7 @@ static void gve_turnup(struct gve_priv *priv)
}

if (priv->tx_cfg.num_xdp_queues && gve_supports_xdp_xmit(priv))
- xdp_features_set_redirect_target(priv->dev, false);
+ xdp_features_set_redirect_target_locked(priv->dev, false);

gve_set_napi_enabled(priv);
}
diff --git a/include/net/xdp.h b/include/net/xdp.h
index 20e41b5ff319..b40f1f96cb11 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -618,7 +618,10 @@ bool bpf_dev_bound_kfunc_id(u32 btf_id);
void xdp_set_features_flag(struct net_device *dev, xdp_features_t val);
void xdp_set_features_flag_locked(struct net_device *dev, xdp_features_t val);
void xdp_features_set_redirect_target(struct net_device *dev, bool support_sg);
+void xdp_features_set_redirect_target_locked(struct net_device *dev,
+ bool support_sg);
void xdp_features_clear_redirect_target(struct net_device *dev);
+void xdp_features_clear_redirect_target_locked(struct net_device *dev);
#else
static inline u32 bpf_xdp_metadata_kfunc_id(int id) { return 0; }
static inline bool bpf_dev_bound_kfunc_id(u32 btf_id) { return false; }
diff --git a/net/core/xdp.c b/net/core/xdp.c
index a014df88620c..ea819764ae39 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -1014,21 +1014,38 @@ void xdp_set_features_flag(struct net_device *dev, xdp_features_t val)
}
EXPORT_SYMBOL_GPL(xdp_set_features_flag);

-void xdp_features_set_redirect_target(struct net_device *dev, bool support_sg)
+void xdp_features_set_redirect_target_locked(struct net_device *dev,
+ bool support_sg)
{
xdp_features_t val = (dev->xdp_features | NETDEV_XDP_ACT_NDO_XMIT);

if (support_sg)
val |= NETDEV_XDP_ACT_NDO_XMIT_SG;
- xdp_set_features_flag(dev, val);
+ xdp_set_features_flag_locked(dev, val);
+}
+EXPORT_SYMBOL_GPL(xdp_features_set_redirect_target_locked);
+
+void xdp_features_set_redirect_target(struct net_device *dev, bool support_sg)
+{
+ netdev_lock(dev);
+ xdp_features_set_redirect_target_locked(dev, support_sg);
+ netdev_unlock(dev);
}
EXPORT_SYMBOL_GPL(xdp_features_set_redirect_target);

-void xdp_features_clear_redirect_target(struct net_device *dev)
+void xdp_features_clear_redirect_target_locked(struct net_device *dev)
{
xdp_features_t val = dev->xdp_features;

val &= ~(NETDEV_XDP_ACT_NDO_XMIT | NETDEV_XDP_ACT_NDO_XMIT_SG);
- xdp_set_features_flag(dev, val);
+ xdp_set_features_flag_locked(dev, val);
+}
+EXPORT_SYMBOL_GPL(xdp_features_clear_redirect_target_locked);
+
+void xdp_features_clear_redirect_target(struct net_device *dev)
+{
+ netdev_lock(dev);
+ xdp_features_clear_redirect_target_locked(dev);
+ netdev_unlock(dev);
}
EXPORT_SYMBOL_GPL(xdp_features_clear_redirect_target);
--
2.49.0.805.g082f7c87e0-goog