UPSTREAM: net/packet: fix a race in packet_set_ring() and packet_notifier()

commit 01d3c8417b9c1b884a8a981a3b886da556512f36 upstream.

When packet_set_ring() releases po->bind_lock, another thread can
run packet_notifier() and process an NETDEV_UP event.

This race and the fix are both similar to that of commit 15fe076e
("net/packet: fix a race in packet_bind() and packet_notifier()").

There too the packet_notifier NETDEV_UP event managed to run while a
po->bind_lock critical section had to be temporarily released. And
the fix was similarly to temporarily set po->num to zero to keep
the socket unhooked until the lock is retaken.

The po->bind_lock in packet_set_ring and packet_notifier precede the
introduction of git history.

Bug: 438674212
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Quang Le <quanglex97@gmail.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250801175423.2970334-1-willemdebruijn.kernel@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit f2e8fcfd2b1bc754920108b7f2cd75082c5a18df)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Ibcc94a6f951a94a6b1a82ebb199b355a1c39a5e1