From: Paolo Abeni <pabeni@xxxxxxxxxx>
At passive MPJ time, if the msk socket lock is held by the user,
the new subflow is appended to the msk->join_list under the msk
data lock.
In mptcp_release_cb()/__mptcp_flush_join_list(), the subflows in
that list are moved from the join_list into the conn_list under the
msk socket lock.
Append and removal could race, possibly corrupting such list.
Address the issue splicing the join list into a temporary one while
still under the msk data lock.
Found by code inspection, the race itself should be almost impossible
to trigger in practice.
Fixes: 3e5014909b56 ("mptcp: cleanup MPJ subflow list handling")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Reviewed-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
Signed-off-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
---
net/mptcp/protocol.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index ee357700b27b..9a40dae31cec 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -850,12 +850,12 @@ static bool __mptcp_finish_join(struct mptcp_sock *msk, struct sock *ssk)
return true;
}
-static void __mptcp_flush_join_list(struct sock *sk)
+static void __mptcp_flush_join_list(struct sock *sk, struct list_head *join_list)
{
struct mptcp_subflow_context *tmp, *subflow;
struct mptcp_sock *msk = mptcp_sk(sk);
- list_for_each_entry_safe(subflow, tmp, &msk->join_list, node) {
+ list_for_each_entry_safe(subflow, tmp, join_list, node) {
struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
bool slow = lock_sock_fast(ssk);
@@ -3342,9 +3342,14 @@ static void mptcp_release_cb(struct sock *sk)
for (;;) {
unsigned long flags = (msk->cb_flags & MPTCP_FLAGS_PROCESS_CTX_NEED) |
msk->push_pending;
+ struct list_head join_list;
+
if (!flags)
break;
+ INIT_LIST_HEAD(&join_list);
+ list_splice_init(&msk->join_list, &join_list);
+
/* the following actions acquire the subflow socket lock
*
* 1) can't be invoked in atomic scope
@@ -3355,8 +3360,9 @@ static void mptcp_release_cb(struct sock *sk)
msk->push_pending = 0;
msk->cb_flags &= ~flags;
spin_unlock_bh(&sk->sk_lock.slock);
+
if (flags & BIT(MPTCP_FLUSH_JOIN_LIST))
- __mptcp_flush_join_list(sk);
+ __mptcp_flush_join_list(sk, &join_list);
if (flags & BIT(MPTCP_PUSH_PENDING))
__mptcp_push_pending(sk, 0);
if (flags & BIT(MPTCP_RETRANSMIT))
--
2.40.1
