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SubjectRe: [syzbot] [kernel?] BUG: unable to handle kernel NULL pointer dereference in hrtimer_active
On Tue, 13 Feb 2024 00:01:03 +0100 Thomas Gleixner wrote:
> So something in that syzbot test case manages to tear down a napi
> context which has not yet been fully initialized. While the rest of
> napi_disable() does not care much as long as neither NAPIF_STATE_SCHED
> nor NAPIF_STATE_NPSVC are set in napi->state, hrtimer_cancel() pretty
> much cares as demonstrated by the NULL pointer dereference.
>
> While it would be trivial to harden the hrtimer code for the case that a
> non-initialized hrtimer is canceled, I wonder whether this invocation of
> napi_disable() is harmless (aside of the hrtimer issue) or if there are
> some hidden subtle issues with that.

Thanks for the forward, I stared at it for a bit and I can see one way
to make veth disable unregistered NAPI. I'll send a fix shortly.

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