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Message-ID: <20230818104031.3890323-1-edumazet@google.com>
Date: Fri, 18 Aug 2023 10:40:31 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>, syzbot <syzkaller@...glegroups.com>
Subject: [PATCH net] ipv4: fix data-races around inet->inet_id
UDP sendmsg() is lockless, so ip_select_ident_segs()
can very well be run from multiple cpus [1]
Convert inet->inet_id to an atomic_t, but implement
a dedicated path for TCP, avoiding cost of a locked
instruction (atomic_add_return())
Note that this patch will cause a trivial merge conflict
because we added inet->flags in net-next tree.
[1]
BUG: KCSAN: data-race in __ip_make_skb / __ip_make_skb
read-write to 0xffff888145af952a of 2 bytes by task 7803 on cpu 1:
ip_select_ident_segs include/net/ip.h:542 [inline]
ip_select_ident include/net/ip.h:556 [inline]
__ip_make_skb+0x844/0xc70 net/ipv4/ip_output.c:1446
ip_make_skb+0x233/0x2c0 net/ipv4/ip_output.c:1560
udp_sendmsg+0x1199/0x1250 net/ipv4/udp.c:1260
inet_sendmsg+0x63/0x80 net/ipv4/af_inet.c:830
sock_sendmsg_nosec net/socket.c:725 [inline]
sock_sendmsg net/socket.c:748 [inline]
____sys_sendmsg+0x37c/0x4d0 net/socket.c:2494
___sys_sendmsg net/socket.c:2548 [inline]
__sys_sendmmsg+0x269/0x500 net/socket.c:2634
__do_sys_sendmmsg net/socket.c:2663 [inline]
__se_sys_sendmmsg net/socket.c:2660 [inline]
__x64_sys_sendmmsg+0x57/0x60 net/socket.c:2660
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
read to 0xffff888145af952a of 2 bytes by task 7804 on cpu 0:
ip_select_ident_segs include/net/ip.h:541 [inline]
ip_select_ident include/net/ip.h:556 [inline]
__ip_make_skb+0x817/0xc70 net/ipv4/ip_output.c:1446
ip_make_skb+0x233/0x2c0 net/ipv4/ip_output.c:1560
udp_sendmsg+0x1199/0x1250 net/ipv4/udp.c:1260
inet_sendmsg+0x63/0x80 net/ipv4/af_inet.c:830
sock_sendmsg_nosec net/socket.c:725 [inline]
sock_sendmsg net/socket.c:748 [inline]
____sys_sendmsg+0x37c/0x4d0 net/socket.c:2494
___sys_sendmsg net/socket.c:2548 [inline]
__sys_sendmmsg+0x269/0x500 net/socket.c:2634
__do_sys_sendmmsg net/socket.c:2663 [inline]
__se_sys_sendmmsg net/socket.c:2660 [inline]
__x64_sys_sendmmsg+0x57/0x60 net/socket.c:2660
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0x184d -> 0x184e
Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7804 Comm: syz-executor.1 Not tainted 6.5.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
==================================================================
Fixes: 23f57406b82d ("ipv4: avoid using shared IP generator for connected sockets")
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/net/inet_sock.h | 2 +-
include/net/ip.h | 15 +++++++++++++--
net/dccp/ipv4.c | 4 ++--
net/ipv4/af_inet.c | 2 +-
net/ipv4/datagram.c | 2 +-
net/ipv4/tcp_ipv4.c | 4 ++--
net/sctp/socket.c | 2 +-
7 files changed, 21 insertions(+), 10 deletions(-)
diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index 0bb32bfc61832dd787abcb2db3ee85d55c83f2c9..491ceb7ebe5d1c6cb502fbcae46c3369f4cb2681 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -222,8 +222,8 @@ struct inet_sock {
__s16 uc_ttl;
__u16 cmsg_flags;
struct ip_options_rcu __rcu *inet_opt;
+ atomic_t inet_id;
__be16 inet_sport;
- __u16 inet_id;
__u8 tos;
__u8 min_ttl;
diff --git a/include/net/ip.h b/include/net/ip.h
index 332521170d9b86ab8cf53e134e199d4312e298cf..19adacd5ece031547e3ad70d524e89d8a6301a55 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -538,8 +538,19 @@ static inline void ip_select_ident_segs(struct net *net, struct sk_buff *skb,
* generator as much as we can.
*/
if (sk && inet_sk(sk)->inet_daddr) {
- iph->id = htons(inet_sk(sk)->inet_id);
- inet_sk(sk)->inet_id += segs;
+ int val;
+
+ /* avoid atomic operations for TCP,
+ * as we hold socket lock at this point.
+ */
+ if (sk_is_tcp(sk)) {
+ sock_owned_by_me(sk);
+ val = atomic_read(&inet_sk(sk)->inet_id);
+ atomic_set(&inet_sk(sk)->inet_id, val + segs);
+ } else {
+ val = atomic_add_return(segs, &inet_sk(sk)->inet_id);
+ }
+ iph->id = htons(val);
return;
}
if ((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) {
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index fa8079303cb060aadb50ec1ae822876198c4ef4a..a545ad71201c87e5a1744c3d6ff8a25e621bca24 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -130,7 +130,7 @@ int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
inet->inet_daddr,
inet->inet_sport,
inet->inet_dport);
- inet->inet_id = get_random_u16();
+ atomic_set(&inet->inet_id, get_random_u16());
err = dccp_connect(sk);
rt = NULL;
@@ -432,7 +432,7 @@ struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
RCU_INIT_POINTER(newinet->inet_opt, rcu_dereference(ireq->ireq_opt));
newinet->mc_index = inet_iif(skb);
newinet->mc_ttl = ip_hdr(skb)->ttl;
- newinet->inet_id = get_random_u16();
+ atomic_set(&newinet->inet_id, get_random_u16());
if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
goto put_and_exit;
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 9b2ca2fcc5a1176ffcaab4abee1492c6466ce5ca..02736b83c30320124cf64721fbe60bb29084e109 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -340,7 +340,7 @@ static int inet_create(struct net *net, struct socket *sock, int protocol,
else
inet->pmtudisc = IP_PMTUDISC_WANT;
- inet->inet_id = 0;
+ atomic_set(&inet->inet_id, 0);
sock_init_data(sock, sk);
diff --git a/net/ipv4/datagram.c b/net/ipv4/datagram.c
index 4d1af0cd7d99e3f76a4202a91e2a4f5869e9aa2f..cb5dbee9e018fbba1bc1e5705e8bec6c4203af56 100644
--- a/net/ipv4/datagram.c
+++ b/net/ipv4/datagram.c
@@ -73,7 +73,7 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
reuseport_has_conns_set(sk);
sk->sk_state = TCP_ESTABLISHED;
sk_set_txhash(sk);
- inet->inet_id = get_random_u16();
+ atomic_set(&inet->inet_id, get_random_u16());
sk_dst_set(sk, &rt->dst);
err = 0;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index a59cc4b8386113577d966a3efce53a13f51e8b06..2dbdc26da86e4389e0debdc46fe4d3acb3df8873 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -312,7 +312,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
inet->inet_daddr));
}
- inet->inet_id = get_random_u16();
+ atomic_set(&inet->inet_id, get_random_u16());
if (tcp_fastopen_defer_connect(sk, &err))
return err;
@@ -1596,7 +1596,7 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
inet_csk(newsk)->icsk_ext_hdr_len = 0;
if (inet_opt)
inet_csk(newsk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
- newinet->inet_id = get_random_u16();
+ atomic_set(&newinet->inet_id, get_random_u16());
/* Set ToS of the new socket based upon the value of incoming SYN.
* ECT bits are set later in tcp_init_transfer().
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 9388d98aebc033f195e56d5295fd998996d41f7e..f791b9c83bf76ab7c5b1541d740c4ebcb5575328 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -9479,7 +9479,7 @@ void sctp_copy_sock(struct sock *newsk, struct sock *sk,
newinet->inet_rcv_saddr = inet->inet_rcv_saddr;
newinet->inet_dport = htons(asoc->peer.port);
newinet->pmtudisc = inet->pmtudisc;
- newinet->inet_id = get_random_u16();
+ atomic_set(&newinet->inet_id, get_random_u16());
newinet->uc_ttl = inet->uc_ttl;
newinet->mc_loop = 1;
--
2.42.0.rc1.204.g551eb34607-goog
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