CVE-2026-80985: net/smc: carry oversized SMC-Rv2 LLC messages in the queue entry
In the Linux kernel, the following vulnerability has been resolved:
net/smc: carry oversized SMC-Rv2 LLC messages in the queue entry
smcllcrmtdeleterkey() and smcllcsaveaddlinkrkeys() read the part of a v2 message that does not fit into the 44-byte union smcllcmsg, and both bound themselves by the size of the buffer it landed in, not by what arrived. On a link with a shared v2 receive buffer a 44-byte DELETERKEYV2 declaring 255 rkeys reaches rkey[9..254] in whatever an earlier message left in lgr->wrrxbufv2, and passes each of them to smcrtokendelete(). One of those 255 matched a registered rtoken and deleted it. An ADDLINK on such a link installs up to 255 rtokens from the same bytes.
Copy the tail into the queue entry, so its length is the length of the message that arrived, and declare the rkeys that fit inline as a member of the union instead of reaching them through a cast. The same DELETERKEYV2 now processes the 9 rkeys it carries. The copy is limited to the longest tail the two functions can read, so the peer does not pick the size of the entry.
The bound the previous patch placed on links without a shared v2 receive buffer is no longer needed.
Affected Software
Event History
Frequently Asked Questions
Which systems are exposed to this issue?
Systems using the Linux kernel's SMC subsystem with SMC-Rv2 links are relevant. The vulnerable behavior specifically involves links that use a shared v2 receive buffer.
What must an attacker control to exploit the flaw?
A peer must be able to send a crafted 44-byte DELETE_RKEY_V2 message that declares 255 rkeys on an affected SMC-Rv2 link. The issue can cause stale bytes from an earlier message in the shared receive buffer to be treated as additional rkeys.
What is the practical impact of a crafted message?
The crafted DELETE_RKEY_V2 message can cause the kernel to process rkeys that were not present in the received message. If one of those stale values matches a registered rtoken, it can be deleted; an ADD_LINK message can similarly install up to 255 rtokens from stale buffer contents.
How can I determine whether a system is affected?
Review whether the running kernel includes the fixes referenced by the listed stable kernel commits. Systems that do not use SMC-Rv2 links are not implicated by the described attack path.