Add a global sx sigio_lock to protect the pointer to the sigio object

of a socket.  This avoids lock order reversal caused by locking a
process in pgsigio().

sowakeup() and the callers of it (sowwakeup, soisconnected, etc.) now
require sigio_lock to be locked.  Provide sowwakeup_locked(),
soisconnected_locked(), and so on in case where we have to modify a
socket and wake up a process atomically.

1 files changed, 5 insertions, 1 deletions

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index c7533e6..09be5d2 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1842,10 +1842,14 @@ process_ACK:
 				 * specification, but if we don't get a FIN
 				 * we'll hang forever.
 				 */
+				SIGIO_SLOCK();
 				if (so->so_state & SS_CANTRCVMORE) {
-					soisdisconnected(so);
+					soisdisconnected_locked(so);
+					SIGIO_SUNLOCK();
 					callout_reset(tp->tt_2msl, tcp_maxidle,
 						      tcp_timer_2msl, tp);
+				} else {
+					SIGIO_SUNLOCK();
 				}
 				tp->t_state = TCPS_FIN_WAIT_2;
 			}