[PATCH 6.1 128/195] mptcp: fix lockless access in subflow ULP diag

Greg Kroah-Hartman
2024-02-27T14:18:17Z

From: Paolo Abeni <pabeni@redhat.com>

commit b8adb69a7d29c2d33eb327bca66476fb6066516b upstream.

Since the introduction of the subflow ULP diag interface, the
dump callback accessed all the subflow data with lockless.

We need either to annotate all the read and write operation accordingly,
or acquire the subflow socket lock. Let's do latter, even if slower, to
avoid a diffstat havoc.

Fixes: 5147dfb50832 ("mptcp: allow dumping subflow context to userspace")
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>
---
include/net/tcp.h | 2 +-
net/mptcp/diag.c | 6 +++++-
net/tls/tls_main.c | 2 +-
3 files changed, 7 insertions(+), 3 deletions(-)

--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2290,7 +2290,7 @@ struct tcp_ulp_ops {
/* cleanup ulp */
void (*release)(struct sock *sk);
/* diagnostic */
- int (*get_info)(const struct sock *sk, struct sk_buff *skb);
+ int (*get_info)(struct sock *sk, struct sk_buff *skb);
size_t (*get_info_size)(const struct sock *sk);
/* clone ulp */
void (*clone)(const struct request_sock *req, struct sock *newsk,
--- a/net/mptcp/diag.c
+++ b/net/mptcp/diag.c
@@ -13,17 +13,19 @@
#include <uapi/linux/mptcp.h>
#include "protocol.h"

-static int subflow_get_info(const struct sock *sk, struct sk_buff *skb)
+static int subflow_get_info(struct sock *sk, struct sk_buff *skb)
{
struct mptcp_subflow_context *sf;
struct nlattr *start;
u32 flags = 0;
+ bool slow;
int err;

start = nla_nest_start_noflag(skb, INET_ULP_INFO_MPTCP);
if (!start)
return -EMSGSIZE;

+ slow = lock_sock_fast(sk);
rcu_read_lock();
sf = rcu_dereference(inet_csk(sk)->icsk_ulp_data);
if (!sf) {
@@ -69,11 +71,13 @@ static int subflow_get_info(const struct
}

rcu_read_unlock();
+ unlock_sock_fast(sk, slow);
nla_nest_end(skb, start);
return 0;

nla_failure:
rcu_read_unlock();
+ unlock_sock_fast(sk, slow);
nla_nest_cancel(skb, start);
return err;
}
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -1098,7 +1098,7 @@ static u16 tls_user_config(struct tls_co
return 0;
}

-static int tls_get_info(const struct sock *sk, struct sk_buff *skb)
+static int tls_get_info(struct sock *sk, struct sk_buff *skb)
{
u16 version, cipher_type;
struct tls_context *ctx;