CVE-2026-93224: svcrdma: Fix unmatched rn_unregister on failed accept

CVE-2026-93224: svcrdma: Fix unmatched rn_unregister on failed accept

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

svcrdma: Fix unmatched rn_unregister on failed accept

When svc_rdma_accept() takes the errout path before
rpcrdma_rn_register() has succeeded, the existing cleanup block
calls rpcrdma_rn_unregister(dev, &newxprt->sc_rn) unconditionally.
svcxprt_rdma is kzalloc'd, so on that path sc_rn.rn_index is 0 and
sc_rn.rn_done is NULL; the unregister therefore xa_erase()s another
caller's slot 0 and performs an unmatched kref_put() on the
rpcrdma_device's rd_kref.

The same errout also brackets the cleanup with svc_xprt_get()/
svc_xprt_put() around the kref_init() birth reference. The kref
goes 1 -> 2 -> 1 and never reaches 0, so the svcxprt_rdma (and the
net/ns_tracker it pinned) is leaked on every failed accept.

rpcrdma_rn_register() writes rn->rn_done last, only after xa_alloc()
and kref_get() have both succeeded, so rn_done == NULL is a natural
"never registered" sentinel. Guard rpcrdma_rn_unregister() with an
early return when rn_done is NULL, and clear rn_done before the
matching xa_erase() so a repeated unregister is also a no-op.

With that guard in place, the accept errout drops the kref_init()
birth reference via svc_xprt_put(), which dispatches svc_rdma_free().
Teardown of sc_qp, sc_sq_cq, sc_rq_cq, and sc_pd runs under existing
IS_ERR/NULL guards in svc_rdma_free(); sc_rn is covered by the new
rn_done sentinel; sc_cm_id is non-NULL on every errout path because
svc_rdma_accept() dereferences it above the first goto errout.

svc_xprt_free() drops the module reference associated with the freed
transport, and svc_handle_xprt() drops its pre-acquired reference
when ->xpo_accept() returns NULL. Take a replacement module reference
before svc_xprt_put() so the two module_put()s remain balanced.

The rn_done guard also covers svc_rdma_free()'s non-listener call
to rpcrdma_rn_unregister() for transports whose register attempt
failed or never ran.

The Linux kernel CVE team has assigned CVE-2026-93224 to this issue.


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

	Issue introduced in 6.12.35 with commit cb3cba0ec372fa7c5f5f5c12990bef02e458ab86 and fixed in 6.12.109 with commit 0335800071a6dfdf7d21d729b5e7d8fa98936211
	Issue introduced in 6.16 with commit 8ac6fcae5dc0e801f1c82a83f5ae2c0a4db19932 and fixed in 6.18.50 with commit 5aabe070c00e5bdf4ab150fb5f72ad5f266d6241
	Issue introduced in 6.16 with commit 8ac6fcae5dc0e801f1c82a83f5ae2c0a4db19932 and fixed in 7.2.4 with commit 45a444a17240f4fa2235f0dfd4a96fc80f1eb2c2
	Issue introduced in 6.16 with commit 8ac6fcae5dc0e801f1c82a83f5ae2c0a4db19932 and fixed in 7.3-rc1 with commit 26190394c64c9429481fc88a4738f70bb92fb352
	Issue introduced in 6.15.4 with commit d310955106c358c8e1ea682defd8e21af44a6cba

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-2026-93224
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:
	net/sunrpc/xprtrdma/ib_client.c
	net/sunrpc/xprtrdma/svc_rdma_transport.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/0335800071a6dfdf7d21d729b5e7d8fa98936211
	https://git.kernel.org/stable/c/5aabe070c00e5bdf4ab150fb5f72ad5f266d6241
	https://git.kernel.org/stable/c/45a444a17240f4fa2235f0dfd4a96fc80f1eb2c2
	https://git.kernel.org/stable/c/26190394c64c9429481fc88a4738f70bb92fb352