From: Florian Fainelli <florian.fainelli@broadcom.com>
To: stable@vger.kernel.org
Cc: Eric Dumazet <edumazet@google.com>,
syzbot+937b5bbb6a815b3e5d0b@syzkaller.appspotmail.com,
Kuniyuki Iwashima <kuniyu@google.com>,
Jakub Kicinski <kuba@kernel.org>,
Florian Fainelli <florian.fainelli@broadcom.com>,
"David S. Miller" <davem@davemloft.net>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
Neal Cardwell <ncardwell@google.com>,
Matthieu Baerts <matttbe@kernel.org>,
Mat Martineau <martineau@kernel.org>,
Geliang Tang <geliang@kernel.org>,
netdev@vger.kernel.org (open list:NETWORKING [GENERAL]),
linux-kernel@vger.kernel.org (open list),
mptcp@lists.linux.dev (open list:NETWORKING [MPTCP]),
bcm-kernel-feedback-list@broadcom.com
Subject: [PATCH stable 5.10.y] tcp: fix potential race in tcp_v6_syn_recv_sock()
Date: Wed, 2 Sep 2026 17:00:26 -0700 [thread overview]
Message-ID: <20260903000029.3508006-1-florian.fainelli@broadcom.com> (raw)
From: Eric Dumazet <edumazet@google.com>
Code in tcp_v6_syn_recv_sock() after the call to tcp_v4_syn_recv_sock()
is done too late.
After tcp_v4_syn_recv_sock(), the child socket is already visible
from TCP ehash table and other cpus might use it.
Since newinet->pinet6 is still pointing to the listener ipv6_pinfo
bad things can happen as syzbot found.
Move the problematic code in tcp_v6_mapped_child_init()
and call this new helper from tcp_v4_syn_recv_sock() before
the ehash insertion.
This allows the removal of one tcp_sync_mss(), since
tcp_v4_syn_recv_sock() will call it with the correct
context.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+937b5bbb6a815b3e5d0b@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/69949275.050a0220.2eeac1.0145.GAE@google.com/
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260217161205.2079883-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
(cherry picked from commit 858d2a4f67ff69e645a43487ef7ea7f28f06deae)
[florian:
- net/ipv6/tcp_ipv6.c:
- Set `newnp->ipv6_fl_list = NULL` instead of `newinet->ipv6_fl_list = NULL`,
as `ipv6_fl_list` is in `struct ipv6_pinfo`.
- Guarded `af_specific` assignment with `#ifdef CONFIG_TCP_MD5SIG` instead
of checking `CONFIG_TCP_AO`.
- Used `if (tcp_inet6_sk(sk)->repflow)` instead of `inet6_test_bit(REPFLOW, sk)`.
- net/smc/af_smc.c:
- Dropped changes to net/smc/af_smc.c because SMC did not implement
`smc_tcp_syn_recv_sock()` in 5.10.y (added in 5.14 via commit e94a869818ab).]
Assisted-by: Cursor:gemini-3.7-flash
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
---
include/net/inet_connection_sock.h | 4 +-
include/net/tcp.h | 4 +-
net/ipv4/syncookies.c | 2 +-
net/ipv4/tcp_fastopen.c | 2 +-
net/ipv4/tcp_ipv4.c | 8 ++-
net/ipv4/tcp_minisocks.c | 2 +-
net/ipv6/tcp_ipv6.c | 98 +++++++++++++-----------------
net/mptcp/subflow.c | 6 +-
8 files changed, 62 insertions(+), 64 deletions(-)
diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index cfb66f5a5076..ba99da8eedb7 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -41,7 +41,9 @@ struct inet_connection_sock_af_ops {
struct request_sock *req,
struct dst_entry *dst,
struct request_sock *req_unhash,
- bool *own_req);
+ bool *own_req,
+ void (*opt_child_init)(struct sock *newsk,
+ const struct sock *sk));
u16 net_header_len;
u16 net_frag_header_len;
u16 sockaddr_len;
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4c87936a33d6..5488e66ee69a 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -438,7 +438,9 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
struct dst_entry *dst,
struct request_sock *req_unhash,
- bool *own_req);
+ bool *own_req,
+ void (*opt_child_init)(struct sock *newsk,
+ const struct sock *sk));
int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
int tcp_connect(struct sock *sk);
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index cc860f2dcf65..29fb93cb3228 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -201,7 +201,7 @@ struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
bool own_req;
child = icsk->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
- NULL, &own_req);
+ NULL, &own_req, NULL);
if (child) {
refcount_set(&req->rsk_refcnt, 1);
tcp_sk(child)->tsoffset = tsoff;
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 92d63cf3e50b..edaa6dabfc3c 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -262,7 +262,7 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk,
bool own_req;
child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
- NULL, &own_req);
+ NULL, &own_req, NULL);
if (!child)
return NULL;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 855cca214a02..f1e10db3d625 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1535,7 +1535,9 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
struct dst_entry *dst,
struct request_sock *req_unhash,
- bool *own_req)
+ bool *own_req,
+ void (*opt_child_init)(struct sock *newsk,
+ const struct sock *sk))
{
struct inet_request_sock *ireq;
bool found_dup_sk = false;
@@ -1591,6 +1593,10 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
}
sk_setup_caps(newsk, dst);
+#if IS_ENABLED(CONFIG_IPV6)
+ if (opt_child_init)
+ opt_child_init(newsk, sk);
+#endif
tcp_ca_openreq_child(newsk, dst);
tcp_sync_mss(newsk, dst_mtu(dst));
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 866055e1b801..876104fe47bf 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -770,7 +770,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
* socket is created, wait for troubles.
*/
child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
- req, &own_req);
+ req, &own_req, NULL);
if (!child)
goto listen_overflow;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 523aa2efdc49..12118d5d98a1 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1217,11 +1217,48 @@ static void tcp_v6_restore_cb(struct sk_buff *skb)
sizeof(struct inet6_skb_parm));
}
+/* Called from tcp_v4_syn_recv_sock() for v6_mapped children. */
+static void tcp_v6_mapped_child_init(struct sock *newsk, const struct sock *sk)
+{
+ struct inet_sock *newinet = inet_sk(newsk);
+ struct ipv6_pinfo *newnp;
+
+ newinet->pinet6 = newnp = tcp_inet6_sk(newsk);
+
+ memcpy(newnp, tcp_inet6_sk(sk), sizeof(struct ipv6_pinfo));
+
+ newnp->saddr = newsk->sk_v6_rcv_saddr;
+
+ inet_csk(newsk)->icsk_af_ops = &ipv6_mapped;
+ if (sk_is_mptcp(newsk))
+ mptcpv6_handle_mapped(newsk, true);
+ newsk->sk_backlog_rcv = tcp_v4_do_rcv;
+#ifdef CONFIG_TCP_MD5SIG
+ tcp_sk(newsk)->af_specific = &tcp_sock_ipv6_mapped_specific;
+#endif
+
+ newnp->ipv6_mc_list = NULL;
+ newnp->ipv6_ac_list = NULL;
+ newnp->ipv6_fl_list = NULL;
+ newnp->pktoptions = NULL;
+ newnp->opt = NULL;
+
+ /* tcp_v4_syn_recv_sock() has initialized newinet->mc_{index,ttl} */
+ newnp->mcast_oif = newinet->mc_index;
+ newnp->mcast_hops = newinet->mc_ttl;
+
+ newnp->rcv_flowinfo = 0;
+ if (tcp_inet6_sk(sk)->repflow)
+ newnp->flow_label = 0;
+}
+
static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
struct dst_entry *dst,
struct request_sock *req_unhash,
- bool *own_req)
+ bool *own_req,
+ void (*opt_child_init)(struct sock *newsk,
+ const struct sock *sk))
{
struct inet_request_sock *ireq;
struct ipv6_pinfo *newnp;
@@ -1237,61 +1274,10 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
#endif
struct flowi6 fl6;
- if (skb->protocol == htons(ETH_P_IP)) {
- /*
- * v6 mapped
- */
-
- newsk = tcp_v4_syn_recv_sock(sk, skb, req, dst,
- req_unhash, own_req);
-
- if (!newsk)
- return NULL;
-
- inet_sk(newsk)->pinet6 = tcp_inet6_sk(newsk);
-
- newinet = inet_sk(newsk);
- newnp = tcp_inet6_sk(newsk);
- newtp = tcp_sk(newsk);
-
- memcpy(newnp, np, sizeof(struct ipv6_pinfo));
-
- newnp->saddr = newsk->sk_v6_rcv_saddr;
-
- inet_csk(newsk)->icsk_af_ops = &ipv6_mapped;
- if (sk_is_mptcp(newsk))
- mptcpv6_handle_mapped(newsk, true);
- newsk->sk_backlog_rcv = tcp_v4_do_rcv;
-#ifdef CONFIG_TCP_MD5SIG
- newtp->af_specific = &tcp_sock_ipv6_mapped_specific;
-#endif
-
- newnp->ipv6_mc_list = NULL;
- newnp->ipv6_ac_list = NULL;
- newnp->ipv6_fl_list = NULL;
- newnp->pktoptions = NULL;
- newnp->opt = NULL;
- newnp->mcast_oif = inet_iif(skb);
- newnp->mcast_hops = ip_hdr(skb)->ttl;
- newnp->rcv_flowinfo = 0;
- if (np->repflow)
- newnp->flow_label = 0;
-
- /*
- * No need to charge this sock to the relevant IPv6 refcnt debug socks count
- * here, tcp_create_openreq_child now does this for us, see the comment in
- * that function for the gory details. -acme
- */
-
- /* It is tricky place. Until this moment IPv4 tcp
- worked with IPv6 icsk.icsk_af_ops.
- Sync it now.
- */
- tcp_sync_mss(newsk, inet_csk(newsk)->icsk_pmtu_cookie);
-
- return newsk;
- }
-
+ if (skb->protocol == htons(ETH_P_IP))
+ return tcp_v4_syn_recv_sock(sk, skb, req, dst,
+ req_unhash, own_req,
+ tcp_v6_mapped_child_init);
ireq = inet_rsk(req);
if (sk_acceptq_is_full(sk))
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index b13cd310882d..c9cf0fdbfbdc 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -532,7 +532,9 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
struct request_sock *req,
struct dst_entry *dst,
struct request_sock *req_unhash,
- bool *own_req)
+ bool *own_req,
+ void (*opt_child_init)(struct sock *newsk,
+ const struct sock *sk))
{
struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk);
struct mptcp_subflow_request_sock *subflow_req;
@@ -582,7 +584,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
create_child:
child = listener->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
- req_unhash, own_req);
+ req_unhash, own_req, opt_child_init);
if (child && *own_req) {
struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);
--
2.34.1
next reply other threads:[~2026-09-03 0:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-03 0:00 Florian Fainelli [this message]
2026-09-03 0:00 ` [PATCH stable 5.15.y] tcp: fix potential race in tcp_v6_syn_recv_sock() Florian Fainelli
2026-09-04 0:00 ` sashiko-bot
2026-09-03 0:00 ` [PATCH stable 6.1.y] " Florian Fainelli
2026-09-04 0:00 ` sashiko-bot
2026-09-03 0:00 ` [PATCH stable 6.6.y] " Florian Fainelli
2026-09-04 0:00 ` sashiko-bot
2026-09-04 0:00 ` [PATCH stable 5.10.y] " sashiko-bot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260903000029.3508006-1-florian.fainelli@broadcom.com \
--to=florian.fainelli@broadcom.com \
--cc=bcm-kernel-feedback-list@broadcom.com \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=geliang@kernel.org \
--cc=horms@kernel.org \
--cc=kuba@kernel.org \
--cc=kuniyu@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=martineau@kernel.org \
--cc=matttbe@kernel.org \
--cc=mptcp@lists.linux.dev \
--cc=ncardwell@google.com \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=stable@vger.kernel.org \
--cc=syzbot+937b5bbb6a815b3e5d0b@syzkaller.appspotmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.