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SubjectRe: [PATCH] tun: avoid double free in tun_free_netdev
On Wed, 8 Dec 2021 11:44:02 -0500 George Kennedy wrote:
> > It looks like a lot of the problem is duplicate unwind.
> > Why does err_free_flow, err_free_stat etc unwinds need to exist if
> > the free_netdev is going to do same thing.
>
> Maybe instead do not call security_tun_dev_free_security(tun->security)
> in err_free_flow if it's going to be done anyway in tun_free_netdev().

That won't be good either. register_netdevice() has multiple failure
modes, it may or may not call the destructor depending on where it
fails. Either the stuff that destructor undoes needs to be moved to
ndo_init (which is what destructor always pairs with), or you can check
dev->reg_state. If dev->reg_state is NETREG_UNREGISTERING that means
the destructor will be caller later.

The ndo_init way is preferable, just cut and past the appropriate lines
preceding registration into a ndo_init callback.

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