CVE-2026-23255net: add proper RCU protection to /proc/net/ptype

Official description

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 packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/e974a10a52618f7f57a4bce173a0ed96acd4e5dc
• https://git.kernel.org/stable/c/002a73470b56848e4c81efeaaedd471e92d66d8d
• https://git.kernel.org/stable/c/dcefd3f0b9ed8288654c75254bdcee8e1085e861
• https://git.kernel.org/stable/c/589a530ae44d0c80f523fcfd1a15af8087f27d35
• https://git.kernel.org/stable/c/f613e8b4afea0cd17c7168e8b00e25bc8d33175d
• https://cert-portal.siemens.com/productcert/html/ssa-019113.html
• https://cert-portal.siemens.com/productcert/html/ssa-457936.html
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html