Push Giant acquisition down into fo_stat() from most callers. Acquire

Giant conditional on debug.mpsafenet in the socket soo_stat() routine,
unconditionally in vn_statfile() for VFS, and otherwise don't acquire
Giant.  Accept an unlocked read in kqueue_stat(), and cryptof_stat() is
a no-op.  Don't acquire Giant in fstat() system call.

Note: in fdescfs, fo_stat() is called while holding Giant due to the VFS
stack sitting on top, and therefore there will still be Giant recursion
in this case.

1 files changed, 5 insertions, 1 deletions

diff --git a/sys/kern/sys_socket.c b/sys/kern/sys_socket.c
index e1de4b7..cbaa587 100644
--- a/sys/kern/sys_socket.c
+++ b/sys/kern/sys_socket.c
@@ -225,9 +225,11 @@ soo_stat(fp, ub, active_cred, td)
 	struct thread *td;
 {
 	struct socket *so = fp->f_data;
+	int error;
 
 	bzero((caddr_t)ub, sizeof (*ub));
 	ub->st_mode = S_IFSOCK;
+	NET_LOCK_GIANT();
 	/*
 	 * If SBS_CANTRCVMORE is set, but there's still data left in the
 	 * receive buffer, the socket is still readable.
@@ -244,7 +246,9 @@ soo_stat(fp, ub, active_cred, td)
 	ub->st_size = so->so_rcv.sb_cc - so->so_rcv.sb_ctl;
 	ub->st_uid = so->so_cred->cr_uid;
 	ub->st_gid = so->so_cred->cr_gid;
-	return ((*so->so_proto->pr_usrreqs->pru_sense)(so, ub));
+	error = (*so->so_proto->pr_usrreqs->pru_sense)(so, ub);
+	NET_UNLOCK_GIANT();
+	return (error);
 }
 
 /*