From b864b67a0d197f59ecf6698940600956ceee2cae Mon Sep 17 00:00:00 2001 From: Mark Johnston Date: Sun, 12 Sep 2021 16:05:49 -0400 Subject: [PATCH] socket: Do not include control messages in FIONREAD return value Some system software expects to be able to read at least the number of bytes returned by FIONREAD. When control messages are counted in this return value, this assumption is violated. Follow Linux and OpenBSD here (as well as our own kevent(EVFILT_READ)) and only return the number of data bytes available. Reported by: avg MFC after: 2 weeks --- sys/kern/sys_socket.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/sys/kern/sys_socket.c b/sys/kern/sys_socket.c index 83dc1cb2622..8cf703ab8eb 100644 --- a/sys/kern/sys_socket.c +++ b/sys/kern/sys_socket.c @@ -206,12 +206,13 @@ soo_ioctl(struct file *fp, u_long cmd, void *data, struct ucred *active_cred, break; case FIONREAD: - /* Unlocked read. */ + SOCK_RECVBUF_LOCK(so); if (SOLISTENING(so)) { error = EINVAL; } else { - *(int *)data = sbavail(&so->so_rcv); + *(int *)data = sbavail(&so->so_rcv) - so->so_rcv.sb_ctl; } + SOCK_RECVBUF_UNLOCK(so); break; case FIONWRITE: