[PATCH 6.1 097/215] mptcp: fix data races on local_id

Greg Kroah-Hartman
2024-03-04T21:47:30Z

From: Paolo Abeni <pabeni@redhat.com>

commit a7cfe776637004a4c938fde78be4bd608c32c3ef upstream.

The local address id is accessed lockless by the NL PM, add
all the required ONCE annotation. There is a caveat: the local
id can be initialized late in the subflow life-cycle, and its
validity is controlled by the local_id_valid flag.

Remove such flag and encode the validity in the local_id field
itself with negative value before initialization. That allows
accessing the field consistently with a single read operation.

Fixes: 0ee4261a3681 ("mptcp: implement mptcp_pm_remove_subflow")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

---
net/mptcp/diag.c | 2 +-
net/mptcp/pm_netlink.c | 6 +++---
net/mptcp/pm_userspace.c | 2 +-
net/mptcp/protocol.c | 2 +-
net/mptcp/protocol.h | 13 +++++++++++--
net/mptcp/subflow.c | 9 +++++----
6 files changed, 22 insertions(+), 12 deletions(-)

--- a/net/mptcp/diag.c
+++ b/net/mptcp/diag.c
@@ -65,7 +65,7 @@ static int subflow_get_info(struct sock
sf->map_data_len) ||
nla_put_u32(skb, MPTCP_SUBFLOW_ATTR_FLAGS, flags) ||
nla_put_u8(skb, MPTCP_SUBFLOW_ATTR_ID_REM, sf->remote_id) ||
- nla_put_u8(skb, MPTCP_SUBFLOW_ATTR_ID_LOC, sf->local_id)) {
+ nla_put_u8(skb, MPTCP_SUBFLOW_ATTR_ID_LOC, subflow_get_local_id(sf))) {
err = -EMSGSIZE;
goto nla_failure;
}
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -799,7 +799,7 @@ static void mptcp_pm_nl_rm_addr_or_subfl
mptcp_for_each_subflow_safe(msk, subflow, tmp) {
struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
int how = RCV_SHUTDOWN | SEND_SHUTDOWN;
- u8 id = subflow->local_id;
+ u8 id = subflow_get_local_id(subflow);

if (rm_type == MPTCP_MIB_RMADDR && subflow->remote_id != rm_id)
continue;
@@ -808,7 +808,7 @@ static void mptcp_pm_nl_rm_addr_or_subfl

pr_debug(" -> %s rm_list_ids[%d]=%u local_id=%u remote_id=%u mpc_id=%u",
rm_type == MPTCP_MIB_RMADDR ? "address" : "subflow",
- i, rm_id, subflow->local_id, subflow->remote_id,
+ i, rm_id, id, subflow->remote_id,
msk->mpc_endpoint_id);
spin_unlock_bh(&msk->pm.lock);
mptcp_subflow_shutdown(sk, ssk, how);
@@ -2028,7 +2028,7 @@ static int mptcp_event_add_subflow(struc
if (WARN_ON_ONCE(!sf))
return -EINVAL;

- if (nla_put_u8(skb, MPTCP_ATTR_LOC_ID, sf->local_id))
+ if (nla_put_u8(skb, MPTCP_ATTR_LOC_ID, subflow_get_local_id(sf)))
return -EMSGSIZE;

if (nla_put_u8(skb, MPTCP_ATTR_REM_ID, sf->remote_id))
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -233,7 +233,7 @@ static int mptcp_userspace_pm_remove_id_

lock_sock(sk);
mptcp_for_each_subflow(msk, subflow) {
- if (subflow->local_id == 0) {
+ if (READ_ONCE(subflow->local_id) == 0) {
has_id_0 = true;
break;
}
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -119,7 +119,7 @@ static int __mptcp_socket_create(struct
subflow->request_mptcp = 1;

/* This is the first subflow, always with id 0 */
- subflow->local_id_valid = 1;
+ WRITE_ONCE(subflow->local_id, 0);
mptcp_sock_graft(msk->first, sk->sk_socket);

return 0;
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -475,7 +475,6 @@ struct mptcp_subflow_context {
can_ack : 1, /* only after processing the remote a key */
disposable : 1, /* ctx can be free at ulp release time */
stale : 1, /* unable to snd/rcv data, do not use for xmit */
- local_id_valid : 1, /* local_id is correctly initialized */
valid_csum_seen : 1; /* at least one csum validated */
enum mptcp_data_avail data_avail;
u32 remote_nonce;
@@ -483,7 +482,7 @@ struct mptcp_subflow_context {
u32 local_nonce;
u32 remote_token;
u8 hmac[MPTCPOPT_HMAC_LEN];
- u8 local_id;
+ s16 local_id; /* if negative not initialized yet */
u8 remote_id;
u8 reset_seen:1;
u8 reset_transient:1;
@@ -529,6 +528,7 @@ mptcp_subflow_ctx_reset(struct mptcp_sub
{
memset(&subflow->reset, 0, sizeof(subflow->reset));
subflow->request_mptcp = 1;
+ WRITE_ONCE(subflow->local_id, -1);
}

static inline u64
@@ -909,6 +909,15 @@ bool mptcp_pm_rm_addr_signal(struct mptc
int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
int mptcp_userspace_pm_get_local_id(struct mptcp_sock *msk, struct mptcp_addr_info *skc);

+static inline u8 subflow_get_local_id(const struct mptcp_subflow_context *subflow)
+{
+ int local_id = READ_ONCE(subflow->local_id);
+
+ if (local_id < 0)
+ return 0;
+ return local_id;
+}
+
void __init mptcp_pm_nl_init(void);
void mptcp_pm_nl_work(struct mptcp_sock *msk);
void mptcp_pm_nl_rm_subflow_received(struct mptcp_sock *msk,
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -489,8 +489,8 @@ do_reset:

static void subflow_set_local_id(struct mptcp_subflow_context *subflow, int local_id)
{
- subflow->local_id = local_id;
- subflow->local_id_valid = 1;
+ WARN_ON_ONCE(local_id < 0 || local_id > 255);
+ WRITE_ONCE(subflow->local_id, local_id);
}

static int subflow_chk_local_id(struct sock *sk)
@@ -499,7 +499,7 @@ static int subflow_chk_local_id(struct s
struct mptcp_sock *msk = mptcp_sk(subflow->conn);
int err;

- if (likely(subflow->local_id_valid))
+ if (likely(subflow->local_id >= 0))
return 0;

err = mptcp_pm_get_local_id(msk, (struct sock_common *)sk);
@@ -1630,6 +1630,7 @@ static struct mptcp_subflow_context *sub
pr_debug("subflow=%p", ctx);

ctx->tcp_sock = sk;
+ WRITE_ONCE(ctx->local_id, -1);

return ctx;
}
@@ -1867,7 +1868,7 @@ static void subflow_ulp_clone(const stru
new_ctx->idsn = subflow_req->idsn;

/* this is the first subflow, id is always 0 */
- new_ctx->local_id_valid = 1;
+ subflow_set_local_id(new_ctx, 0);
} else if (subflow_req->mp_join) {
new_ctx->ssn_offset = subflow_req->ssn_offset;
new_ctx->mp_join = 1;