CVE-2026-23255

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.

Affected Software

Weaknesses

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

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