5.15-stable review patch. If anyone has any objections, please let me know.
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From: Jakub Kicinski kuba@kernel.org
[ Upstream commit fe9f801355f0b47668419f30f1fac1cf4539e736 ]
veth sets NETIF_F_GRO automatically when XDP is enabled, because both features use the same NAPI machinery.
The logic to clear NETIF_F_GRO sits in veth_disable_xdp() which is called both on ndo_stop and when XDP is turned off. To avoid the flag from being cleared when the device is brought down, the clearing is skipped when IFF_UP is not set. Bringing the device down should indeed not modify its features.
Unfortunately, this means that clearing is also skipped when XDP is disabled _while_ the device is down. And there's nothing on the open path to bring the device features back into sync. IOW if user enables XDP, disables it and then brings the device up we'll end up with a stray GRO flag set but no NAPI instances.
We don't depend on the GRO flag on the datapath, so the datapath won't crash. We will crash (or hang), however, next time features are sync'ed (either by user via ethtool or peer changing its config). The GRO flag will go away, and veth will try to disable the NAPIs. But the open path never created them since XDP was off, the GRO flag was a stray. If NAPI was initialized before we'll hang in napi_disable(). If it never was we'll crash trying to stop uninitialized hrtimer.
Move the GRO flag updates to the XDP enable / disable paths, instead of mixing them with the ndo_open / ndo_close paths.
Fixes: d3256efd8e8b ("veth: allow enabling NAPI even without XDP") Reported-by: Thomas Gleixner tglx@linutronix.de Reported-by: syzbot+039399a9b96297ddedca@syzkaller.appspotmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Reviewed-by: Toke Høiland-Jørgensen toke@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/veth.c | 35 +++++++++++++++++------------------ 1 file changed, 17 insertions(+), 18 deletions(-)
diff --git a/drivers/net/veth.c b/drivers/net/veth.c index 984a153804096..85c3e12f83627 100644 --- a/drivers/net/veth.c +++ b/drivers/net/veth.c @@ -1079,14 +1079,6 @@ static int veth_enable_xdp(struct net_device *dev) veth_disable_xdp_range(dev, 0, dev->real_num_rx_queues, true); return err; } - - if (!veth_gro_requested(dev)) { - /* user-space did not require GRO, but adding XDP - * is supposed to get GRO working - */ - dev->features |= NETIF_F_GRO; - netdev_features_change(dev); - } } }
@@ -1106,18 +1098,9 @@ static void veth_disable_xdp(struct net_device *dev) for (i = 0; i < dev->real_num_rx_queues; i++) rcu_assign_pointer(priv->rq[i].xdp_prog, NULL);
- if (!netif_running(dev) || !veth_gro_requested(dev)) { + if (!netif_running(dev) || !veth_gro_requested(dev)) veth_napi_del(dev);
- /* if user-space did not require GRO, since adding XDP - * enabled it, clear it now - */ - if (!veth_gro_requested(dev) && netif_running(dev)) { - dev->features &= ~NETIF_F_GRO; - netdev_features_change(dev); - } - } - veth_disable_xdp_range(dev, 0, dev->real_num_rx_queues, false); }
@@ -1497,6 +1480,14 @@ static int veth_xdp_set(struct net_device *dev, struct bpf_prog *prog, }
if (!old_prog) { + if (!veth_gro_requested(dev)) { + /* user-space did not require GRO, but adding + * XDP is supposed to get GRO working + */ + dev->features |= NETIF_F_GRO; + netdev_features_change(dev); + } + peer->hw_features &= ~NETIF_F_GSO_SOFTWARE; peer->max_mtu = max_mtu; } @@ -1507,6 +1498,14 @@ static int veth_xdp_set(struct net_device *dev, struct bpf_prog *prog, if (dev->flags & IFF_UP) veth_disable_xdp(dev);
+ /* if user-space did not require GRO, since adding XDP + * enabled it, clear it now + */ + if (!veth_gro_requested(dev)) { + dev->features &= ~NETIF_F_GRO; + netdev_features_change(dev); + } + if (peer) { peer->hw_features |= NETIF_F_GSO_SOFTWARE; peer->max_mtu = ETH_MAX_MTU;