Re: [PATCH net] ipv6: ndisc: fix NULL deref in accept_untracked_na()

["Weiming Shi" <bestswngs@gmail.com>]

On Wed Jun 17, 2026 at 4:32 PM CST, Jiayuan Chen wrote:
>
> On 6/17/26 2:55 PM, Weiming Shi wrote:
>> accept_untracked_na() re-fetches the inet6_dev with __in6_dev_get(dev)
>> and dereferences idev->cnf.accept_untracked_na without a NULL check,
>
>
> Does ipv6_rpl_srh_rcv have same problem?

Hi,

Yes, ipv6_rpl_srh_rcv() has the same missing check. It reads
idev->cnf.rpl_seg_enabled right after __in6_dev_get(skb->dev) with no
NULL check, while seg6 and ioam6 in the same file both check it.

But I tried to trigger it and couldn't. With a guard added as an instrument,
idev never came back NULL over tens of millions of RPL packets while
flapping the MTU, so I can't say it's actually reachable.

Still, it's the only one of the three without the check. Want me to send
a patch adding it there too, for consistency?

Thanks,
Weiming Shi