Messages in this thread | | | Date | Thu, 5 Jan 2023 12:26:29 -0800 (PST) | From | Mat Martineau <> | Subject | Re: [PATCH] mptcp: Fix deadlock in mptcp_sendmsg() |
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On Fri, 6 Jan 2023, Shigeru Yoshida wrote:
> __mptcp_close_ssk() can be called from mptcp_sendmsg() with subflow > socket locked. This can cause a deadlock as below: > > mptcp_sendmsg() > mptcp_sendmsg_fastopen() --> lock ssk > tcp_sendmsg_fastopen() > __inet_stream_connect() > mptcp_disconnect() > mptcp_destroy_common() > __mptcp_close_ssk() --> lock ssk again > > This patch fixes the issue by skipping locking for subflow socket > which is already locked. >
Hi Shigeru -
I believe this has already been fixed by:
7d803344fdc3 ("mptcp: fix deadlock in fastopen error path")
It is in the net repo:
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git
...but hasn't been merged to net-next or Linus' tree yet. Jakub said to expect a net PR today, which should get the fix both upstream and in to net-next.
Thanks,
Mat
> Fixes: d98a82a6afc7 ("mptcp: handle defer connect in mptcp_sendmsg") > Signed-off-by: Shigeru Yoshida <syoshida@redhat.com> > --- > net/mptcp/protocol.c | 15 +++++++++------ > net/mptcp/protocol.h | 4 ++-- > 2 files changed, 11 insertions(+), 8 deletions(-) > > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c > index f6f93957275b..979265f66082 100644 > --- a/net/mptcp/protocol.c > +++ b/net/mptcp/protocol.c > @@ -1672,9 +1672,9 @@ static int mptcp_sendmsg_fastopen(struct sock *sk, struct sock *ssk, struct msgh > lock_sock(ssk); > msg->msg_flags |= MSG_DONTWAIT; > msk->connect_flags = O_NONBLOCK; > - msk->is_sendmsg = 1; > + msk->sendmsg_locked_sk = ssk; > ret = tcp_sendmsg_fastopen(ssk, msg, copied_syn, len, NULL); > - msk->is_sendmsg = 0; > + msk->sendmsg_locked_sk = NULL; > msg->msg_flags = saved_flags; > release_sock(ssk); > > @@ -2319,7 +2319,8 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, > if (dispose_it) > list_del(&subflow->node); > > - lock_sock_nested(ssk, SINGLE_DEPTH_NESTING); > + if (msk->sendmsg_locked_sk != ssk) > + lock_sock_nested(ssk, SINGLE_DEPTH_NESTING); > > if (flags & MPTCP_CF_FASTCLOSE) { > /* be sure to force the tcp_disconnect() path, > @@ -2335,7 +2336,8 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, > tcp_disconnect(ssk, 0); > msk->subflow->state = SS_UNCONNECTED; > mptcp_subflow_ctx_reset(subflow); > - release_sock(ssk); > + if (msk->sendmsg_locked_sk != ssk) > + release_sock(ssk); > > goto out; > } > @@ -2362,7 +2364,8 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, > /* close acquired an extra ref */ > __sock_put(ssk); > } > - release_sock(ssk); > + if (msk->sendmsg_locked_sk != ssk) > + release_sock(ssk); > > sock_put(ssk); > > @@ -3532,7 +3535,7 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) > /* if reaching here via the fastopen/sendmsg path, the caller already > * acquired the subflow socket lock, too. > */ > - if (msk->is_sendmsg) > + if (msk->sendmsg_locked_sk) > err = __inet_stream_connect(ssock, uaddr, addr_len, msk->connect_flags, 1); > else > err = inet_stream_connect(ssock, uaddr, addr_len, msk->connect_flags); > diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h > index 955fb3d88eb3..43afc399e16b 100644 > --- a/net/mptcp/protocol.h > +++ b/net/mptcp/protocol.h > @@ -294,8 +294,7 @@ struct mptcp_sock { > u8 mpc_endpoint_id; > u8 recvmsg_inq:1, > cork:1, > - nodelay:1, > - is_sendmsg:1; > + nodelay:1; > int connect_flags; > struct work_struct work; > struct sk_buff *ooo_last_skb; > @@ -318,6 +317,7 @@ struct mptcp_sock { > u32 setsockopt_seq; > char ca_name[TCP_CA_NAME_MAX]; > struct mptcp_sock *dl_next; > + struct sock *sendmsg_locked_sk; > }; > > #define mptcp_data_lock(sk) spin_lock_bh(&(sk)->sk_lock.slock) > -- > 2.39.0 > >
-- Mat Martineau Intel
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