[PATCH v5 net 4/5] ipv6: Fix data races around sk->sk_prot.

From: Kuniyuki Iwashima
Date: Thu Oct 06 2022 - 15:16:23 EST


Commit 086d49058cd8 ("ipv6: annotate some data-races around sk->sk_prot")
fixed some data-races around sk->sk_prot but it was not enough.

Some functions in inet6_(stream|dgram)_ops still access sk->sk_prot
without lock_sock() or rtnl_lock(), so they need READ_ONCE() to avoid
load tearing.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
---
net/core/sock.c | 6 ++++--
net/ipv4/af_inet.c | 23 ++++++++++++++++-------
net/ipv6/ipv6_sockglue.c | 4 ++--
3 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index eeb6cbac6f49..a3ba0358c77c 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3610,7 +3610,8 @@ int sock_common_getsockopt(struct socket *sock, int level, int optname,
{
struct sock *sk = sock->sk;

- return sk->sk_prot->getsockopt(sk, level, optname, optval, optlen);
+ /* IPV6_ADDRFORM can change sk->sk_prot under us. */
+ return READ_ONCE(sk->sk_prot)->getsockopt(sk, level, optname, optval, optlen);
}
EXPORT_SYMBOL(sock_common_getsockopt);

@@ -3636,7 +3637,8 @@ int sock_common_setsockopt(struct socket *sock, int level, int optname,
{
struct sock *sk = sock->sk;

- return sk->sk_prot->setsockopt(sk, level, optname, optval, optlen);
+ /* IPV6_ADDRFORM can change sk->sk_prot under us. */
+ return READ_ONCE(sk->sk_prot)->setsockopt(sk, level, optname, optval, optlen);
}
EXPORT_SYMBOL(sock_common_setsockopt);

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index e2c219382345..3dd02396517d 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -558,22 +558,27 @@ int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr,
int addr_len, int flags)
{
struct sock *sk = sock->sk;
+ const struct proto *prot;
int err;

if (addr_len < sizeof(uaddr->sa_family))
return -EINVAL;
+
+ /* IPV6_ADDRFORM can change sk->sk_prot under us. */
+ prot = READ_ONCE(sk->sk_prot);
+
if (uaddr->sa_family == AF_UNSPEC)
- return sk->sk_prot->disconnect(sk, flags);
+ return prot->disconnect(sk, flags);

if (BPF_CGROUP_PRE_CONNECT_ENABLED(sk)) {
- err = sk->sk_prot->pre_connect(sk, uaddr, addr_len);
+ err = prot->pre_connect(sk, uaddr, addr_len);
if (err)
return err;
}

if (data_race(!inet_sk(sk)->inet_num) && inet_autobind(sk))
return -EAGAIN;
- return sk->sk_prot->connect(sk, uaddr, addr_len);
+ return prot->connect(sk, uaddr, addr_len);
}
EXPORT_SYMBOL(inet_dgram_connect);

@@ -734,10 +739,11 @@ EXPORT_SYMBOL(inet_stream_connect);
int inet_accept(struct socket *sock, struct socket *newsock, int flags,
bool kern)
{
- struct sock *sk1 = sock->sk;
+ struct sock *sk1 = sock->sk, *sk2;
int err = -EINVAL;
- struct sock *sk2 = sk1->sk_prot->accept(sk1, flags, &err, kern);

+ /* IPV6_ADDRFORM can change sk->sk_prot under us. */
+ sk2 = READ_ONCE(sk1->sk_prot)->accept(sk1, flags, &err, kern);
if (!sk2)
goto do_err;

@@ -825,12 +831,15 @@ ssize_t inet_sendpage(struct socket *sock, struct page *page, int offset,
size_t size, int flags)
{
struct sock *sk = sock->sk;
+ const struct proto *prot;

if (unlikely(inet_send_prepare(sk)))
return -EAGAIN;

- if (sk->sk_prot->sendpage)
- return sk->sk_prot->sendpage(sk, page, offset, size, flags);
+ /* IPV6_ADDRFORM can change sk->sk_prot under us. */
+ prot = READ_ONCE(sk->sk_prot);
+ if (prot->sendpage)
+ return prot->sendpage(sk, page, offset, size, flags);
return sock_no_sendpage(sock, page, offset, size, flags);
}
EXPORT_SYMBOL(inet_sendpage);
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index a20edae868fd..d7207a546aec 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -477,7 +477,7 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
sock_prot_inuse_add(net, sk->sk_prot, -1);
sock_prot_inuse_add(net, &tcp_prot, 1);

- /* Paired with READ_ONCE(sk->sk_prot) in net/ipv6/af_inet6.c */
+ /* Paired with READ_ONCE(sk->sk_prot) in inet6_stream_ops */
WRITE_ONCE(sk->sk_prot, &tcp_prot);
icsk->icsk_af_ops = &ipv4_specific;
sk->sk_socket->ops = &inet_stream_ops;
@@ -492,7 +492,7 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
sock_prot_inuse_add(net, sk->sk_prot, -1);
sock_prot_inuse_add(net, prot, 1);

- /* Paired with READ_ONCE(sk->sk_prot) in net/ipv6/af_inet6.c */
+ /* Paired with READ_ONCE(sk->sk_prot) in inet6_dgram_ops */
WRITE_ONCE(sk->sk_prot, prot);
sk->sk_socket->ops = &inet_dgram_ops;
sk->sk_family = PF_INET;
--
2.30.2