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Sat, 11 Jul 2026 06:18:32 -0700 (PDT) From: Weiming Shi To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, dsahern@gmail.com Cc: kuniyu@google.com, gnault@redhat.com, xmei5@asu.edu, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Weiming Shi Subject: [PATCH net] mpls: fix NULL deref in mpls_valid_fib_dump_req() on CONFIG_INET=n Date: Sat, 11 Jul 2026 04:50:00 -0700 Message-ID: <20260711114958.1009619-3-bestswngs@gmail.com> 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: 8bit 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. Fixes: 196cfebf8972 ("net/mpls: Handle kernel side filtering of route dumps") Assisted-by: Claude:claude-opus-4-8 Reported-by: Xiang Mei Signed-off-by: Weiming Shi --- net/mpls/af_mpls.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c index ca504d9626cf..318cb7e2ac5f 100644 --- a/net/mpls/af_mpls.c +++ b/net/mpls/af_mpls.c @@ -2186,6 +2186,9 @@ static int mpls_valid_fib_dump_req(struct net *net, const struct nlmsghdr *nlh, int ifindex; if (i == RTA_OIF) { + if (!tb[i]) + continue; + ifindex = nla_get_u32(tb[i]); filter->dev = dev_get_by_index_rcu(net, ifindex); if (!filter->dev) -- 2.43.0