[PATCH net 1/2] net/smc: transfer fasync_list in case of fallback

[Karsten Graul <kgraul@linux.ibm.com>]

From: Ursula Braun <ubraun@linux.ibm.com>

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@syzkaller.appspotmail.com
Fixes: ee9dfbef02d18 ("net/smc: handle sockopts forcing fallback")
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
---
 net/smc/af_smc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index cee5bf4a9bb9..90988a511cd5 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -470,6 +470,8 @@ static void smc_switch_to_fallback(struct smc_sock *smc)
 	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;
 	}
 }
 
-- 
2.17.1