CVE-2026-68425: IB/mad: Drop unmatched RMPP responses before reassembly

From: Greg Kroah-Hartman <[email protected]>

Description
===========

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

IB/mad: Drop unmatched RMPP responses before reassembly

Kernel-handled RMPP receive processing starts reassembly for active
DATA responses before the response is matched to an outstanding send.
The normal match happens later, after ib_process_rmpp_recv_wc() has
either assembled a complete message or consumed the segment.

That ordering lets an unsolicited response that routes to a kernel
RMPP agent by the high TID bits allocate or extend RMPP receive state
before the full TID and source address are checked against a real
request. A reordered burst can therefore reach the receive-side
insertion path even though the response would not match any send.

For kernel-handled RMPP DATA responses, require the existing
ib_find_send_mad() match before entering RMPP reassembly. The matcher
already checks the full TID, management class and source address/GID
against the agent wait, backlog and in-flight send lists. If there is
no match, drop the response without creating RMPP state.

This leaves the RMPP window behavior unchanged and only rejects
responses that have no corresponding request.

The Linux kernel CVE team has assigned CVE-2026-68425 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.13 with commit fa619a77046bef30478697aba0553991033afb8e and fixed in 6.6.148 with commit dfa535c94406c03d3f0c869ef3ba5528e395737c
	Issue introduced in 2.6.13 with commit fa619a77046bef30478697aba0553991033afb8e and fixed in 6.12.101 with commit 6e1bd7f590b0ccfee07f7fe1d48b92059bd37d72
	Issue introduced in 2.6.13 with commit fa619a77046bef30478697aba0553991033afb8e and fixed in 6.18.42 with commit 98d2d468b4faa1fdc68c0c6c238389906ee3490c
	Issue introduced in 2.6.13 with commit fa619a77046bef30478697aba0553991033afb8e and fixed in 7.1.6 with commit ad9c9ad3204f63a46f0f7de29687a8e512f05e29
	Issue introduced in 2.6.13 with commit fa619a77046bef30478697aba0553991033afb8e and fixed in 7.2-rc4 with commit d2e52d610b9b09694261632340b801a421e0b0c5

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-68425
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/infiniband/core/mad.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/dfa535c94406c03d3f0c869ef3ba5528e395737c
	https://git.kernel.org/stable/c/6e1bd7f590b0ccfee07f7fe1d48b92059bd37d72
	https://git.kernel.org/stable/c/98d2d468b4faa1fdc68c0c6c238389906ee3490c
	https://git.kernel.org/stable/c/ad9c9ad3204f63a46f0f7de29687a8e512f05e29
	https://git.kernel.org/stable/c/d2e52d610b9b09694261632340b801a421e0b0c5