net/mptcp/protocol.c | 15 +++++++++------ net/mptcp/protocol.h | 4 ++-- 2 files changed, 11 insertions(+), 8 deletions(-)
__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.
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
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
On Thu, Jan 05, 2023 at 12:26:29PM -0800, Mat Martineau wrote: > 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 Hi Mat, Thank you so much for your prompt response. I've missed above patch. Yes, the patch fixed the same issue. Thank you~ Shigeru > > ...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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