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([2601:282:1e02:1040:c495:5538:b9fc:6fc5]) by smtp.googlemail.com with ESMTPSA id 46e09a7af769-7ebcb2b79c9sm8973682a34.22.2026.07.11.09.56.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 11 Jul 2026 09:56:43 -0700 (PDT) Message-ID: <5cf2d4ee-376f-4baa-baf1-fd7bf7500251@gmail.com> Date: Sat, 11 Jul 2026 10:56:42 -0600 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] mpls: fix NULL deref in mpls_valid_fib_dump_req() on CONFIG_INET=n Content-Language: en-US To: Weiming Shi , davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Cc: kuniyu@google.com, gnault@redhat.com, xmei5@asu.edu, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260711114958.1009619-3-bestswngs@gmail.com> From: David Ahern In-Reply-To: <20260711114958.1009619-3-bestswngs@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/11/26 5:50 AM, Weiming Shi wrote: > 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) Reviewed-by: David Ahern