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

Summary

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.

Timeline

1. Mar 18, 2026, 5:41 PM UTCCVE published
2. Oct 15, 2026, 1:13 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in e974a10a52618f7f57a4bce173a0ed96acd4e5dc; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 002a73470b56848e4c81efeaaedd471e92d66d8d; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in dcefd3f0b9ed8288654c75254bdcee8e1085e861; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 589a530ae44d0c80f523fcfd1a15af8087f27d35; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in f613e8b4afea0cd17c7168e8b00e25bc8d33175d

• Linux Linux

  2.6.12

• KernelLinux

  From 2.6.12 · fixed in 6.1.175; From 6.2.0 · fixed in 6.6.136; From 6.7.0 · fixed in 6.12.80; From 6.13.0 · fixed in 6.18.10

References 5