[PATCH 5.4 088/152] net/smc: transfer fasync_list in case of fallback

[Greg Kroah-Hartman]

From: Ursula Braun <ubraun@xxxxxxxxxxxxx>

commit 67f562e3e147750a02b2a91d21a163fc44a1d13e upstream.

SMC does not work together with FASTOPEN. If sendmsg() is called with
flag MSG_FASTOPEN in SMC_INIT state, the SMC-socket switches to
fallback mode. To handle the previous ioctl FIOASYNC call correctly
in this case, it is necessary to transfer the socket wait queue
fasync_list to the internal TCP socket.

Reported-by: syzbot+4b1fe8105f8044a26162@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: ee9dfbef02d18 ("net/smc: handle sockopts forcing fallback")
Signed-off-by: Ursula Braun <ubraun@xxxxxxxxxxxxx>
Signed-off-by: Karsten Graul <kgraul@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 net/smc/af_smc.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -467,6 +467,8 @@ static void smc_switch_to_fallback(struc
 	if (smc->sk.sk_socket && smc->sk.sk_socket->file) {
 		smc->clcsock->file = smc->sk.sk_socket->file;
 		smc->clcsock->file->private_data = smc->clcsock;
+		smc->clcsock->wq.fasync_list =
+			smc->sk.sk_socket->wq.fasync_list;
 	}
 }