This is a note to let you know that I've just added the patch titled

netfilter: on sockopt() acquire sock lock only in the required scope

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: netfilter-on-sockopt-acquire-sock-lock-only-in-the-required-scope.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 3f34cfae1238848fd53f25e5c8fd59da57901f4b Mon Sep 17 00:00:00 2001

From: Paolo Abeni pabeni@redhat.com Date: Tue, 30 Jan 2018 19:01:40 +0100 Subject: netfilter: on sockopt() acquire sock lock only in the required scope

From: Paolo Abeni pabeni@redhat.com

commit 3f34cfae1238848fd53f25e5c8fd59da57901f4b upstream.

Syzbot reported several deadlocks in the netfilter area caused by rtnl lock and socket lock being acquired with a different order on different code paths, leading to backtraces like the following one:

====================================================== WARNING: possible circular locking dependency detected 4.15.0-rc9+ #212 Not tainted ------------------------------------------------------ syzkaller041579/3682 is trying to acquire lock: (sk_lock-AF_INET6){+.+.}, at: [<000000008775e4dd>] lock_sock include/net/sock.h:1463 [inline] (sk_lock-AF_INET6){+.+.}, at: [<000000008775e4dd>] do_ipv6_setsockopt.isra.8+0x3c5/0x39d0 net/ipv6/ipv6_sockglue.c:167

but task is already holding lock: (rtnl_mutex){+.+.}, at: [<000000004342eaa9>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (rtnl_mutex){+.+.}: __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 register_netdevice_notifier+0xad/0x860 net/core/dev.c:1607 tee_tg_check+0x1a0/0x280 net/netfilter/xt_TEE.c:106 xt_check_target+0x22c/0x7d0 net/netfilter/x_tables.c:845 check_target net/ipv6/netfilter/ip6_tables.c:538 [inline] find_check_entry.isra.7+0x935/0xcf0 net/ipv6/netfilter/ip6_tables.c:580 translate_table+0xf52/0x1690 net/ipv6/netfilter/ip6_tables.c:749 do_replace net/ipv6/netfilter/ip6_tables.c:1165 [inline] do_ip6t_set_ctl+0x370/0x5f0 net/ipv6/netfilter/ip6_tables.c:1691 nf_sockopt net/netfilter/nf_sockopt.c:106 [inline] nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115 ipv6_setsockopt+0x115/0x150 net/ipv6/ipv6_sockglue.c:928 udpv6_setsockopt+0x45/0x80 net/ipv6/udp.c:1422 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978 SYSC_setsockopt net/socket.c:1849 [inline] SyS_setsockopt+0x189/0x360 net/socket.c:1828 entry_SYSCALL_64_fastpath+0x29/0xa0

-> #0 (sk_lock-AF_INET6){+.+.}: lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3914 lock_sock_nested+0xc2/0x110 net/core/sock.c:2780 lock_sock include/net/sock.h:1463 [inline] do_ipv6_setsockopt.isra.8+0x3c5/0x39d0 net/ipv6/ipv6_sockglue.c:167 ipv6_setsockopt+0xd7/0x150 net/ipv6/ipv6_sockglue.c:922 udpv6_setsockopt+0x45/0x80 net/ipv6/udp.c:1422 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978 SYSC_setsockopt net/socket.c:1849 [inline] SyS_setsockopt+0x189/0x360 net/socket.c:1828 entry_SYSCALL_64_fastpath+0x29/0xa0

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1 ---- ---- lock(rtnl_mutex); lock(sk_lock-AF_INET6); lock(rtnl_mutex); lock(sk_lock-AF_INET6);

*** DEADLOCK ***

1 lock held by syzkaller041579/3682: #0: (rtnl_mutex){+.+.}, at: [<000000004342eaa9>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74

The problem, as Florian noted, is that nf_setsockopt() is always called with the socket held, even if the lock itself is required only for very tight scopes and only for some operation.

This patch addresses the issues moving the lock_sock() call only where really needed, namely in ipv*_getorigdst(), so that nf_setsockopt() does not need anymore to acquire both locks.

Fixes: 22265a5c3c10 ("netfilter: xt_TEE: resolve oif using netdevice notifiers") Reported-by: syzbot+a4c2dc980ac1af699b36@syzkaller.appspotmail.com Suggested-by: Florian Westphal fw@strlen.de Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- net/ipv4/ip_sockglue.c | 14 ++++---------- net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c | 6 +++++- net/ipv6/ipv6_sockglue.c | 17 +++++------------ net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c | 18 ++++++++++++------ 4 files changed, 26 insertions(+), 29 deletions(-)

--- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -1251,11 +1251,8 @@ int ip_setsockopt(struct sock *sk, int l if (err == -ENOPROTOOPT && optname != IP_HDRINCL && optname != IP_IPSEC_POLICY && optname != IP_XFRM_POLICY && - !ip_mroute_opt(optname)) { - lock_sock(sk); + !ip_mroute_opt(optname)) err = nf_setsockopt(sk, PF_INET, optname, optval, optlen); - release_sock(sk); - } #endif return err; } @@ -1280,12 +1277,9 @@ int compat_ip_setsockopt(struct sock *sk if (err == -ENOPROTOOPT && optname != IP_HDRINCL && optname != IP_IPSEC_POLICY && optname != IP_XFRM_POLICY && - !ip_mroute_opt(optname)) { - lock_sock(sk); - err = compat_nf_setsockopt(sk, PF_INET, optname, - optval, optlen); - release_sock(sk); - } + !ip_mroute_opt(optname)) + err = compat_nf_setsockopt(sk, PF_INET, optname, optval, + optlen); #endif return err; } --- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c +++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c @@ -218,15 +218,19 @@ getorigdst(struct sock *sk, int optval, struct nf_conntrack_tuple tuple;

memset(&tuple, 0, sizeof(tuple)); + + lock_sock(sk); tuple.src.u3.ip = inet->inet_rcv_saddr; tuple.src.u.tcp.port = inet->inet_sport; tuple.dst.u3.ip = inet->inet_daddr; tuple.dst.u.tcp.port = inet->inet_dport; tuple.src.l3num = PF_INET; tuple.dst.protonum = sk->sk_protocol; + release_sock(sk);

/* We only do TCP and SCTP at the moment: is there a better way? */ - if (sk->sk_protocol != IPPROTO_TCP && sk->sk_protocol != IPPROTO_SCTP) { + if (tuple.dst.protonum != IPPROTO_TCP && + tuple.dst.protonum != IPPROTO_SCTP) { pr_debug("SO_ORIGINAL_DST: Not a TCP/SCTP socket\n"); return -ENOPROTOOPT; } --- a/net/ipv6/ipv6_sockglue.c +++ b/net/ipv6/ipv6_sockglue.c @@ -915,12 +915,8 @@ int ipv6_setsockopt(struct sock *sk, int #ifdef CONFIG_NETFILTER /* we need to exclude all possible ENOPROTOOPTs except default case */ if (err == -ENOPROTOOPT && optname != IPV6_IPSEC_POLICY && - optname != IPV6_XFRM_POLICY) { - lock_sock(sk); - err = nf_setsockopt(sk, PF_INET6, optname, optval, - optlen); - release_sock(sk); - } + optname != IPV6_XFRM_POLICY) + err = nf_setsockopt(sk, PF_INET6, optname, optval, optlen); #endif return err; } @@ -950,12 +946,9 @@ int compat_ipv6_setsockopt(struct sock * #ifdef CONFIG_NETFILTER /* we need to exclude all possible ENOPROTOOPTs except default case */ if (err == -ENOPROTOOPT && optname != IPV6_IPSEC_POLICY && - optname != IPV6_XFRM_POLICY) { - lock_sock(sk); - err = compat_nf_setsockopt(sk, PF_INET6, optname, - optval, optlen); - release_sock(sk); - } + optname != IPV6_XFRM_POLICY) + err = compat_nf_setsockopt(sk, PF_INET6, optname, optval, + optlen); #endif return err; } --- a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c +++ b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c @@ -226,20 +226,27 @@ static const struct nf_hook_ops ipv6_con static int ipv6_getorigdst(struct sock *sk, int optval, void __user *user, int *len) { - const struct inet_sock *inet = inet_sk(sk); + struct nf_conntrack_tuple tuple = { .src.l3num = NFPROTO_IPV6 }; const struct ipv6_pinfo *inet6 = inet6_sk(sk); + const struct inet_sock *inet = inet_sk(sk); const struct nf_conntrack_tuple_hash *h; struct sockaddr_in6 sin6; - struct nf_conntrack_tuple tuple = { .src.l3num = NFPROTO_IPV6 }; struct nf_conn *ct; + __be32 flow_label; + int bound_dev_if;

+ lock_sock(sk); tuple.src.u3.in6 = sk->sk_v6_rcv_saddr; tuple.src.u.tcp.port = inet->inet_sport; tuple.dst.u3.in6 = sk->sk_v6_daddr; tuple.dst.u.tcp.port = inet->inet_dport; tuple.dst.protonum = sk->sk_protocol; + bound_dev_if = sk->sk_bound_dev_if; + flow_label = inet6->flow_label; + release_sock(sk);

- if (sk->sk_protocol != IPPROTO_TCP && sk->sk_protocol != IPPROTO_SCTP) + if (tuple.dst.protonum != IPPROTO_TCP && + tuple.dst.protonum != IPPROTO_SCTP) return -ENOPROTOOPT;

if (*len < 0 || (unsigned int) *len < sizeof(sin6)) @@ -257,14 +264,13 @@ ipv6_getorigdst(struct sock *sk, int opt

sin6.sin6_family = AF_INET6; sin6.sin6_port = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u.tcp.port; - sin6.sin6_flowinfo = inet6->flow_label & IPV6_FLOWINFO_MASK; + sin6.sin6_flowinfo = flow_label & IPV6_FLOWINFO_MASK; memcpy(&sin6.sin6_addr, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.in6, sizeof(sin6.sin6_addr));

nf_ct_put(ct); - sin6.sin6_scope_id = ipv6_iface_scope_id(&sin6.sin6_addr, - sk->sk_bound_dev_if); + sin6.sin6_scope_id = ipv6_iface_scope_id(&sin6.sin6_addr, bound_dev_if); return copy_to_user(user, &sin6, sizeof(sin6)) ? -EFAULT : 0; }

Patches currently in stable-queue which might be from pabeni@redhat.com are

queue-4.14/netfilter-on-sockopt-acquire-sock-lock-only-in-the-required-scope.patch