Re: [PATCH v3 20/28] net: do not delete nics in net_cleanup()

["Durrant, Paul" <xadimgnik@xxxxxxxxx>]

On 25/10/2023 15:50, David Woodhouse wrote:
> From: David Woodhouse <dwmw@xxxxxxxxxxxx>
>
> In net_cleanup() we only need to delete the netdevs, as those may have
> state which outlives Qemu when it exits, and thus may actually need to
> be cleaned up on exit.
>
> The nics, on the other hand, are owned by the device which created them.
> Most devices don't bother to clean up on exit because they don't have
> any state which will outlive Qemu... but XenBus devices do need to clean
> up their nodes in XenStore, and do have an exit handler to delete them.
>
> When the XenBus exit handler destroys the xen-net-device, it attempts
> to delete its nic after net_cleanup() had already done so. And crashes.
>
> Fix this by only deleting netdevs as we walk the list. As the comment
> notes, we can't use QTAILQ_FOREACH_SAFE() as each deletion may remove
> *multiple* entries, including the "safely" saved 'next' pointer. But
> we can store the *previous* entry, since nics are safe.
>
> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> ---
>   net/net.c | 28 ++++++++++++++++++++++------
>   1 file changed, 22 insertions(+), 6 deletions(-)
Reviewed-by: Paul Durrant <paul@xxxxxxx>