CVE-2026-89784: SUNRPC: check rpc_sockaddr2uaddr() return value in rpcb_register_inet4/6

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

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

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

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

SUNRPC: check rpc_sockaddr2uaddr() return value in rpcb_register_inet4/6

rpcb_register_inet4() and rpcb_register_inet6() store the result of
rpc_sockaddr2uaddr() into map->r_addr without checking it for NULL.
rpc_sockaddr2uaddr() returns NULL when its final kstrdup() fails, and
the unchecked NULL is then carried into the synchronous RPCBPROC_SET
encode path: rpcb_register_call() -> rpc_call_sync() ->
rpcb_enc_getaddr() -> encode_rpcb_string(), whose first statement is
strlen(string), dereferencing NULL and oopsing the kernel.

The crash reproduces under failslab on v6.12; with KASAN the NULL
dereference surfaces as a fault on the shadow of address zero:

 Oops: general protection fault, probably for non-canonical address
       0xdffffc0000000000 [#1] PREEMPT SMP KASAN
 RIP: 0010:strlen (lib/string.c:409)
 Call Trace:
  encode_rpcb_string (net/sunrpc/rpcb_clnt.c:890)
  rpcb_enc_getaddr (net/sunrpc/rpcb_clnt.c:910)
  rpcauth_wrap_req_encode (net/sunrpc/auth.c:745)
  call_encode (net/sunrpc/clnt.c:1966)
  __rpc_execute (net/sunrpc/sched.c:952)
  rpc_run_task (net/sunrpc/clnt.c:1243)
  rpc_call_sync (net/sunrpc/clnt.c:1272)
  rpcb_v4_register (net/sunrpc/rpcb_clnt.c:500)
  svc_generic_rpcbind_set
  nfsd_rpcbind_set
  svc_register
  svc_setup_socket
  svc_addsock
  write_ports
  nfsctl_transaction_write
  vfs_write

The crash is reachable when an in-kernel RPC service (nfsd, lockd,
nfs-callback) registers with the local rpcbind under enough memory
pressure for the small GFP_KERNEL kstrdup() in rpc_sockaddr2uaddr() to
fail. The asynchronous getport path already handles this exact failure
mode by returning -ENOMEM; only the two register helpers omit the check.

Mirror that handling: bail out with -ENOMEM when rpc_sockaddr2uaddr()
returns NULL, before the address is fed into the encoder.

The Linux kernel CVE team has assigned CVE-2026-89784 to this issue.


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

	Issue introduced in 3.2 with commit d77385f23830ee6c400569bac8b37e6eb3b7d360 and fixed in 5.10.270 with commit 04441b792ec40eb66349b5fab34b6a2090b5b2dd
	Issue introduced in 3.2 with commit d77385f23830ee6c400569bac8b37e6eb3b7d360 and fixed in 5.15.221 with commit 5a51c49ddb37b883566874aecc66bc5a2e617a96
	Issue introduced in 3.2 with commit d77385f23830ee6c400569bac8b37e6eb3b7d360 and fixed in 6.1.188 with commit 4a6095de8cb1858e05bdf70b3e7d6d7645c25041
	Issue introduced in 3.2 with commit d77385f23830ee6c400569bac8b37e6eb3b7d360 and fixed in 6.6.157 with commit 12bf3e0182ccdaf3b412756a756d3944a7dacaa9
	Issue introduced in 3.2 with commit d77385f23830ee6c400569bac8b37e6eb3b7d360 and fixed in 6.12.110 with commit 4e01022974355732e748ec8ebc97c558cb624ffe
	Issue introduced in 3.2 with commit d77385f23830ee6c400569bac8b37e6eb3b7d360 and fixed in 6.18.52 with commit cda4aacfb0bbf5c0f90fd0b42c72c749635d1368
	Issue introduced in 3.2 with commit d77385f23830ee6c400569bac8b37e6eb3b7d360 and fixed in 7.2.6 with commit eb476289c12cc22c8766f8a84eeb7ab46c4e8fb6
	Issue introduced in 3.2 with commit d77385f23830ee6c400569bac8b37e6eb3b7d360 and fixed in 7.3-rc1 with commit fd22370226a0d8109045d0831fd5aaadee921693

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-2026-89784
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/rpcb_clnt.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/04441b792ec40eb66349b5fab34b6a2090b5b2dd
	https://git.kernel.org/stable/c/5a51c49ddb37b883566874aecc66bc5a2e617a96
	https://git.kernel.org/stable/c/4a6095de8cb1858e05bdf70b3e7d6d7645c25041
	https://git.kernel.org/stable/c/12bf3e0182ccdaf3b412756a756d3944a7dacaa9
	https://git.kernel.org/stable/c/4e01022974355732e748ec8ebc97c558cb624ffe
	https://git.kernel.org/stable/c/cda4aacfb0bbf5c0f90fd0b42c72c749635d1368
	https://git.kernel.org/stable/c/eb476289c12cc22c8766f8a84eeb7ab46c4e8fb6
	https://git.kernel.org/stable/c/fd22370226a0d8109045d0831fd5aaadee921693