CVE-2025-38721

In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: fix refcount leak on table dump There is a reference count leak in ctnetlink_dump_table(): if (res < 0) { nf_conntrack_get(&ct->ct_general); // HERE cb->args[1] = (unsigned long)ct; ... While its very unlikely, its possible that ct == last. If this happens, then the refcount of ct was already incremented. This 2nd increment is never undone. This prevents the conntrack object from being released, which in turn keeps prevents cnet->count from dropping back to 0. This will then block the netns dismantle (or conntrack rmmod) as nf_conntrack_cleanup_net_list() will wait forever. This can be reproduced by running conntrack_resize.sh selftest in a loop. It takes ~20 minutes for me on a preemptible kernel on average before I see a runaway kworker spinning in nf_conntrack_cleanup_net_list. One fix would to change this to: if (res < 0) { if (ct != last) nf_conntrack_get(&ct->ct_general); But this reference counting isn't needed in the first place. We can just store a cookie value instead. A followup patch will do the same for ctnetlink_exp_dump_table, it looks to me as if this has the same problem and like ctnetlink_dump_table, we only need a 'skip hint', not the actual object so we can apply the same cookie strategy there as well.

• linux linux kernel (>= 2.6.19 < 5.4.297) • linux linux kernel (>= 5.5 < 5.10.241) • linux linux kernel (>= 5.11 < 5.15.190) • linux linux kernel (>= 5.16 < 6.1.149) • linux linux kernel (>= 6.2 < 6.6.103) • linux linux kernel (>= 6.7 < 6.12.43) • linux linux kernel (>= 6.13 < 6.15.11) • linux linux kernel (>= 6.16 < 6.16.2) • linux linux kernel 2.6.18 • linux linux kernel 6.17 • debian debian linux 11.0