CVE-2026-93231: lockd: fix swapped arguments in nlmsvc_match_ip()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

lockd: fix swapped arguments in nlmsvc_match_ip()

When releasing locks by server IP address via /proc/fs/nfsd/unlock_ip,
nlmsvc_unlock_all_by_ip() calls nlm_traverse_files() with the server
sockaddr as the opaque @data argument:

	nlm_traverse_files(server_addr, nlmsvc_match_ip, NULL);

The match callback is later invoked from nlm_traverse_locks() as:

	match(lockhost, host);

where the first argument is the nlm_host that owns the lock, and the
second argument is the @data that was originally passed down (here the
server sockaddr).  This is the convention every other match callback
relies on (nlmsvc_mark_host(), nlmsvc_same_host(), nlmsvc_is_client()):
arg1 is the real nlm_host, arg2 is the caller-supplied reference value.

nlmsvc_match_ip() has had these two arguments reversed ever since the
unlock-by-IP feature was introduced in commit 4373ea84c84d ("lockd:
unlock lockd locks associated with a given server ip"):

	return rpc_cmp_addr(nlm_srcaddr(host), datap);

Here @host is actually the server sockaddr, so nlm_srcaddr(host)
dereferences a struct sockaddr as a struct nlm_host and reads garbage
at the offset of h_srcaddr; meanwhile @datap is actually the lock
owner's nlm_host but is compared as a sockaddr.  As a result the
comparison practically never matches and locks are not released for the
requested IP.

Swap the arguments so the lock owner's source address is compared
against the requested server address:

	return rpc_cmp_addr(nlm_srcaddr(datap), (struct sockaddr *)host);

[ cel: fix the misleading typedef parameter names too ]

The Linux kernel CVE team has assigned CVE-2026-93231 to this issue.


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

	Issue introduced in 2.6.26 with commit 4373ea84c84d8a96e99d3da99e813d3e36d1bd11 and fixed in 6.18.51 with commit 0d72e78c9d38d5377a059a4837f82b65b91cdcf6
	Issue introduced in 2.6.26 with commit 4373ea84c84d8a96e99d3da99e813d3e36d1bd11 and fixed in 7.2.4 with commit 21bcb609e0ab1dd60f39ca3498f85808933bcc9f
	Issue introduced in 2.6.26 with commit 4373ea84c84d8a96e99d3da99e813d3e36d1bd11 and fixed in 7.3-rc1 with commit b9060689f49dc663e9a3d069c4a65ff63a836e66

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-2026-93231
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:
	fs/lockd/lockd.h
	fs/lockd/svcsubs.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/0d72e78c9d38d5377a059a4837f82b65b91cdcf6
	https://git.kernel.org/stable/c/21bcb609e0ab1dd60f39ca3498f85808933bcc9f
	https://git.kernel.org/stable/c/b9060689f49dc663e9a3d069c4a65ff63a836e66