CVE-2026-89536: SUNRPC: wait for in-flight client TLS handshake callback

CVE-2026-89536: SUNRPC: wait for in-flight client TLS handshake callback

[Greg Kroah-Hartman]

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

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

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

SUNRPC: wait for in-flight client TLS handshake callback

xs_tls_handshake_sync() gives xs_tls_handshake_done() a reference to the
lower transport before submitting the handshake request. On timeout or
signal, the synchronous waiter drops that reference after calling
tls_handshake_cancel().

handshake_req_cancel() returns false when handshake_complete() has
already marked the request complete. In that case the completion callback
can still be running, so dropping the callback-owned reference in the
waiter can free the lower transport before xs_tls_handshake_done() stores
xprt_err or drops its own reference.

If cancellation loses to completion, wait until xs_tls_handshake_done()
signals handshake_done and let the callback release its reference. This
mirrors the server-side handshake lifetime handling and keeps the timeout
or signal return value unchanged.

The Linux kernel CVE team has assigned CVE-2026-89536 to this issue.


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

	Issue introduced in 6.5 with commit 75eb6af7acdf566c68d61e98e67ee2f235201c02 and fixed in 6.12.109 with commit 15431820f448e09f8029b670d5c82aa5917d4625
	Issue introduced in 6.5 with commit 75eb6af7acdf566c68d61e98e67ee2f235201c02 and fixed in 6.18.50 with commit 1de391e8b94e31b45c19c16dbf315e294810c7de
	Issue introduced in 6.5 with commit 75eb6af7acdf566c68d61e98e67ee2f235201c02 and fixed in 7.2.4 with commit 7fbb6d2ab0391eb8d1f1a68e6bc263ef02cea61b
	Issue introduced in 6.5 with commit 75eb6af7acdf566c68d61e98e67ee2f235201c02 and fixed in 7.3-rc1 with commit a89dd597458848b463d284b15e42a8078beeb046

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-2026-89536
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/xprtsock.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/15431820f448e09f8029b670d5c82aa5917d4625
	https://git.kernel.org/stable/c/1de391e8b94e31b45c19c16dbf315e294810c7de
	https://git.kernel.org/stable/c/7fbb6d2ab0391eb8d1f1a68e6bc263ef02cea61b
	https://git.kernel.org/stable/c/a89dd597458848b463d284b15e42a8078beeb046