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.

https://git.kernel.org/stable/c/06db79411a280707c7e4bf4b221ff4e664b51502

https://git.kernel.org/stable/c/56d96fededd61192cd7cc8d2b0f36adfd59036c3

https://git.kernel.org/stable/c/5f6e7b32bd1fbde10fd31a4143260735ea535b8a

https://git.kernel.org/stable/c/ad6284ced6a15e4abd57ca4d0793b7bd15ca52ce

https://git.kernel.org/stable/c/d6eee7cd078aaf9dd75efc801f6c9b608a37cd71

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