On 18-05-2025 09:17, Saurabh Sengar wrote:
The MANA driver's probe registers netdevice via the following call chain:
mana_probe()
register_netdev()
register_netdevice()
register_netdevice() calls notifier callback for netvsc driver,
holding the netdev mutex via netdev_lock_ops().
Further this netvsc notifier callback end up attempting to acquire the
same lock again in dev_xdp_propagate() leading to deadlock.
netvsc_netdev_event()
netvsc_vf_setxdp()
dev_xdp_propagate()
This deadlock was not observed so far because net_shaper_ops was never
set and this lock in noop in this case. Fix this by using
netif_xdp_propagate instead of dev_xdp_propagate to avoid recursive
locking in this path.
This issue has not observed so far because net_shaper_ops was unset,
making the lock path effectively a no-op. To prevent recursive locking
and avoid this deadlock, replace dev_xdp_propagate() with
netif_xdp_propagate(), which does not acquire the lock again.
avoid noop and repetition (because the paragraph about net_shaper_ops is
repeated):
"This deadlock was not observed so far because net_shaper_ops was never
set, and thus the lock was effectively a no-op in this case. Fix this by
using netif_xdp_propagate() instead of dev_xdp_propagate() to avoid
recursive locking in this path.
Also, clean up the unregistration path by removing the unnecessary call
to netvsc_vf_setxdp(), since unregister_netdevice_many_notify() already
performs this cleanup via dev_xdp_uninstall()."
Also, clean up the unregistration path by removing unnecessary call to
netvsc_vf_setxdp(), since unregister_netdevice_many_notify() already
performs this cleanup via dev_xdp_uninstall.
Fixes: 97246d6d21c2 ("net: hold netdev instance lock during ndo_bpf")
Cc: sta...@vger.kernel.org
Signed-off-by: Saurabh Sengar <ssen...@linux.microsoft.com>
---
drivers/net/hyperv/netvsc_bpf.c | 2 +-
drivers/net/hyperv/netvsc_drv.c | 2 --
net/core/dev.c | 1 +
3 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/net/hyperv/netvsc_bpf.c b/drivers/net/hyperv/netvsc_bpf.c
index e01c5997a551..1dd3755d9e6d 100644
--- a/drivers/net/hyperv/netvsc_bpf.c
+++ b/drivers/net/hyperv/netvsc_bpf.c
@@ -183,7 +183,7 @@ int netvsc_vf_setxdp(struct net_device *vf_netdev, struct
bpf_prog *prog)
Thanks,
Alok
