CVE-2026-64569: mpls: fix NULL deref in mpls_valid_fib_dump_req() on CONFIG_INET=n

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

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

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

mpls: fix NULL deref in mpls_valid_fib_dump_req() on CONFIG_INET=n

On CONFIG_INET=n builds, mpls_valid_fib_dump_req() walks the parsed
attribute table itself instead of calling ip_valid_fib_dump_req(). The
RTA_OIF arm passes tb[RTA_OIF] to nla_get_u32() without checking it is
present, so an RTM_GETROUTE dump for AF_MPLS with strict checking and no
RTA_OIF hits a NULL dereference.

RTM_GETROUTE is RTNL_KIND_GET, which rtnetlink_rcv_msg() permits without
CAP_NET_ADMIN, so an unprivileged user can trigger it.

  Oops: general protection fault, probably for non-canonical address
        0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
  KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
  RIP: 0010:mpls_valid_fib_dump_req (net/mpls/af_mpls.c:2189)
  Call Trace:
   mpls_dump_routes (net/mpls/af_mpls.c:2236)
   netlink_dump (net/netlink/af_netlink.c:2331)
   __netlink_dump_start (net/netlink/af_netlink.c:2446)
   rtnetlink_rcv_msg (net/core/rtnetlink.c:7033)
   netlink_rcv_skb (net/netlink/af_netlink.c:2556)
   netlink_unicast (net/netlink/af_netlink.c:1345)
   netlink_sendmsg (net/netlink/af_netlink.c:1900)
   __sock_sendmsg (net/socket.c:790)
   ____sys_sendmsg (net/socket.c:2684)
   ___sys_sendmsg (net/socket.c:2738)
   __sys_sendmsg (net/socket.c:2770)
   do_syscall_64 (arch/x86/entry/syscall_64.c:94)
   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)

Skip unset attributes, as ip_valid_fib_dump_req() does.

The Linux kernel CVE team has assigned CVE-2026-64569 to this issue.


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

	Issue introduced in 4.20 with commit 196cfebf897266c3450519e916bab9daff74e52c and fixed in 6.6.148 with commit d6eee7cd078aaf9dd75efc801f6c9b608a37cd71
	Issue introduced in 4.20 with commit 196cfebf897266c3450519e916bab9daff74e52c and fixed in 6.12.101 with commit ad6284ced6a15e4abd57ca4d0793b7bd15ca52ce
	Issue introduced in 4.20 with commit 196cfebf897266c3450519e916bab9daff74e52c and fixed in 6.18.42 with commit 5f6e7b32bd1fbde10fd31a4143260735ea535b8a
	Issue introduced in 4.20 with commit 196cfebf897266c3450519e916bab9daff74e52c and fixed in 7.1.6 with commit 06db79411a280707c7e4bf4b221ff4e664b51502
	Issue introduced in 4.20 with commit 196cfebf897266c3450519e916bab9daff74e52c and fixed in 7.2-rc4 with commit 56d96fededd61192cd7cc8d2b0f36adfd59036c3

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-2026-64569
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/mpls/af_mpls.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/d6eee7cd078aaf9dd75efc801f6c9b608a37cd71
	https://git.kernel.org/stable/c/ad6284ced6a15e4abd57ca4d0793b7bd15ca52ce
	https://git.kernel.org/stable/c/5f6e7b32bd1fbde10fd31a4143260735ea535b8a
	https://git.kernel.org/stable/c/06db79411a280707c7e4bf4b221ff4e664b51502
	https://git.kernel.org/stable/c/56d96fededd61192cd7cc8d2b0f36adfd59036c3