Re: [PATCH net] net: phy: reject attach while the PHY driver is in transition

[Aleksei Sviridkin <f@lex.la>]

I need to correct what I wrote earlier, because it decides the tree.

What was seen on hardware, with no instrumentation, is the class of
bug: an MT7981 board running an OpenWrt 6.18 kernel, with the distro's
backports and local patches plus the series I was testing on top,
oopsed twice on a NULL phydev->drv after a sysfs unbind of the PHY
driver, once inside a running phy_attach_direct() (in the driver's
config_init) and once in the PHY state machine. I was unbinding on
purpose, racing it against port teardown and bring-up, to stress that
series; none of this shows up in normal operation.

The dereference this patch prevents is a narrower member of that
family: drv already NULL when the attach starts. That window is the
short stretch between phy_remove()'s last store and
device_unbind_cleanup(), and the board never hit it on its own; the
msleep() was needed to reach it at all. So "the msleep() only made the
race deterministic" in my previous mail was wrong. The patch closes the
entry to that window; the wider race, an unbind landing mid-attach, is
untouched.

I will put all of that in the commit log. With both facts on the table,
net with the Fixes tag or net-next is your call.