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SubjectRe: kernel BUG at net/core/net-sysfs.c:LINE!
On Mon, Mar 25, 2019 at 06:10:31PM +0200, Andy Shevchenko wrote:
> On Mon, Mar 25, 2019 at 11:20:01PM +0800, wanghai (M) wrote:
> > thanks , Can it be fixed like this?
>
> I dunno. I think no, it can't.

I agree, it can't.

>
> As far as I can see the issue happened due to freeing entire network device at
> the point of putting reference count to the device (struct device is embedded
> into struct net_device).
>
> When it happens the access to _any_ field of struct net_device will crash the
> system.
>
> Basically it means that put_device() should be carefully placed case-by-case,
> because on real hardware the actual device is parent and usually no-one does
> access to the child without need. On the contrary the tunX devices are
> artificial and are controlled by the network stack.
>
> So, it means we need to do something like
>
> ret = register_netdev(...);
> if (ret) {
> put_device(&ndev->dev);
> ...
> }
>
> But as I mentioned, it would be tricky to not break something else.

I'd say that the entity that called alloc_netdev() should be the one
that calls put_device() (but the way of free_netdev()), not net/core
code. Do we have a driver that is messed up and does not do proper
cleanup?

Thanks.

--
Dmitry

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