CVE-2026-23255

About vulnerability

In the Linux kernel, the following vulnerability has been resolved:

net: add proper RCU protection to /proc/net/ptype

Yin Fengwei reported an RCU stall in ptype_seq_show() and provided a patch.

Real issue is that ptype_seq_next() and ptype_seq_show() violate RCU rules.

ptype_seq_show() runs under rcu_read_lock(), and reads pt->dev to get device name without any barrier.

At the same time, concurrent writers can remove a packet_type structure (which is correctly freed after an RCU grace period) and clear pt->dev without an RCU grace period.

Define ptype_iter_state to carry a dev pointer along seq_net_private:

struct ptype_iter_state { struct seq_net_private p; struct net_device *dev; // added in this patch };

We need to record the device pointer in ptype_get_idx() and ptype_seq_next() so that ptype_seq_show() is safe against concurrent pt->dev changes.

We also need to add full RCU protection in ptype_seq_next(). (Missing READ_ONCE() when reading list.next values)

Many thanks to Dong Chenchen for providing a repro.

Affected product:

AlmaLinux 9.2 ESU , Amazon Linux 2 ELS , CentOS 6 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Debian 10 ELS , Oracle Linux 6 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS

Affected packages:

kernel-uek @ 5.4.17 (+17 more)

Live-patch status from KernelCare for each operating system.