Re: [PATCH] netfilter: conntrack: drop expectations before freeing templates

Florian Westphal
2025-08-20T00:17:13Z

Qingjie Xing <xqjcool@gmail.com> wrote:
> With an iptables-configured TFTP helper in place, a UDP packet
> (10.65.41.36:1069 → 10.65.36.2:69, TFTP RRQ) triggered creation of an expectation.
> Later, iptables changes removed the rule’s per-rule template nf_conn.
> When the expectation’s timer expired, nf_ct_unlink_expect_report()
> ran and dereferenced the freed master, causing a crash.

Sorry, I do not see the problem.
A template should never be listed as exp->master.

Can you make a reproducer/selftest for this bug?

I worry we paper over a different bug.