CVE-2026-90067

Summary

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

libceph: validate banner payload length

When parsing the Ceph messenger v2 protocol banner, the payload_len field is decoded from the banner prefix. If a client sends a banner with a payload_len of 0, the kernel sets up a 0-length socket read. This violates an invariant in the state machine, triggering a warning in populate_in_iter():

————[ cut here ]———— !iov_iter_count(&con->v2.in_iter) WARNING: net/ceph/messenger_v2.c:3129 at populate_in_iter net/ceph/messenger_v2.c:3129 [inline], CPU#1: kworker/1:3/5070 WARNING: net/ceph/messenger_v2.c:3129 at ceph_con_v2_try_read+0x6634/0x6810 net/ceph/messenger_v2.c:3159, CPU#1: kworker/1:3/5070 … Call Trace: <TASK> ceph_con_workfn+0x1f5/0x14a0 net/ceph/messenger.c:1575 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK>

According to the msgr2 protocol specification, the banner payload is expected to contain at least two 64-bit integers (server_feat and server_req_feat). Therefore, payload_len must be at least 16 bytes.

Fix this by adding a check in process_banner_prefix() to reject a payload_len smaller than 16 bytes. This prevents the 0-length read and correctly aborts the connection with a protocol error.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/279c0852999fd2384f4a88155091a99e81f96873
• https://git.kernel.org/stable/c/6cf666e47f2b51d5a887ec8a3226cde951757d27
• https://git.kernel.org/stable/c/3b2e62a7655d347a845a91155610ddae11daffc6
• https://git.kernel.org/stable/c/c1b937ff24b19e69aa7fb1b0f46a74d4c9668692
• https://git.kernel.org/stable/c/6d1c6f228854aa89844fd0152d7ed7ac72a55e89
• https://git.kernel.org/stable/c/c77633a9595658210a6e216a071e5a396a0835a7
• https://git.kernel.org/stable/c/f374967fcdf04001c9b66df1c19106fa83cd91f7

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