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([2607:fb90:eca4:601:96a2:dc03:fbca:601e]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ccc9d5bdddsm88368665ad.77.2026.07.12.15.09.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Jul 2026 15:09:05 -0700 (PDT) From: Xiang Mei To: "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: David Ahern , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bestswngs@gmail.com, Xiang Mei Subject: [PATCH net] mpls: fix NULL deref in mpls_valid_fib_dump_req() on CONFIG_INET=n Date: Sun, 12 Jul 2026 15:09:03 -0700 Message-ID: <20260712220903.3131568-1-xmei5@asu.edu> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" On CONFIG_INET=3Dn, mpls_valid_fib_dump_req()'s local strict-check loop enters the RTA_OIF arm on the index alone and calls nla_get_u32(tb[i]). Since nlmsg_parse_deprecated_strict() leaves tb[i] NULL for any omitted attribute, a dump without RTA_OIF dereferences NULL and oopses. Skip unset attributes before dispatching on the index, mirroring ip_valid_fib_dump_req(). 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:7041) 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) Kernel panic - not syncing: Fatal exception Fixes: 196cfebf8972 ("net/mpls: Handle kernel side filtering of route dumps= ") Reported-by: Weiming Shi Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei Reviewed-by: David Ahern --- net/mpls/af_mpls.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c index ca504d9626cf..1ad07df89d5b 100644 --- a/net/mpls/af_mpls.c +++ b/net/mpls/af_mpls.c @@ -2185,13 +2185,16 @@ static int mpls_valid_fib_dump_req(struct net *net,= const struct nlmsghdr *nlh, for (i =3D 0; i <=3D RTA_MAX; ++i) { int ifindex; =20 + if (!tb[i]) + continue; + if (i =3D=3D RTA_OIF) { ifindex =3D nla_get_u32(tb[i]); filter->dev =3D dev_get_by_index_rcu(net, ifindex); if (!filter->dev) return -ENODEV; filter->filter_set =3D 1; - } else if (tb[i]) { + } else { NL_SET_ERR_MSG_MOD(extack, "Unsupported attribute in dump request"); return -EINVAL; } --=20 2.43.0