Make linprocfs(5) report correct tty number in /proc/<PID>/stat.

Fixes sudo (sudo-1.8.21p2-3ubuntu1.2); previously would fail
with "sudo: no tty present and no askpass program specified".

Reviewed by:	kib, emaste
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D25588

1 files changed, 29 insertions, 4 deletions

diff --git a/sys/compat/linprocfs/linprocfs.c b/sys/compat/linprocfs/linprocfs.c
index d0f5e2dd4404..c3d7eafd9492 100644
--- a/sys/compat/linprocfs/linprocfs.c
+++ b/sys/compat/linprocfs/linprocfs.c
@@ -767,6 +767,32 @@ linprocfs_doloadavg(PFS_FILL_ARGS)
 	return (0);
 }
 
+static int
+linprocfs_get_tty_nr(struct proc *p)
+{
+	struct session *sp;
+	const char *ttyname;
+	int error, major, minor, nr;
+
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+	sx_assert(&proctree_lock, SX_LOCKED);
+
+	if ((p->p_flag & P_CONTROLT) == 0)
+		return (-1);
+
+	sp = p->p_pgrp->pg_session;
+	if (sp == NULL)
+		return (-1);
+
+	ttyname = devtoname(sp->s_ttyp->t_dev);
+	error = linux_driver_get_major_minor(ttyname, &major, &minor);
+	if (error != 0)
+		return (-1);
+
+	nr = makedev(major, minor);
+	return (nr);
+}
+
 /*
  * Filler function for proc/pid/stat
  */
@@ -777,12 +803,14 @@ linprocfs_doprocstat(PFS_FILL_ARGS)
 	struct timeval boottime;
 	char state;
 	static int ratelimit = 0;
+	int tty_nr;
 	vm_offset_t startcode, startdata;
 
 	getboottime(&boottime);
 	sx_slock(&proctree_lock);
 	PROC_LOCK(p);
 	fill_kinfo_proc(p, &kp);
+	tty_nr = linprocfs_get_tty_nr(p);
 	sx_sunlock(&proctree_lock);
 	if (p->p_vmspace) {
 	   startcode = (vm_offset_t)p->p_vmspace->vm_taddr;
@@ -809,10 +837,7 @@ linprocfs_doprocstat(PFS_FILL_ARGS)
 	PS_ADD("pgrp",		"%d",	p->p_pgid);
 	PS_ADD("session",	"%d",	p->p_session->s_sid);
 	PROC_UNLOCK(p);
-	if (kp.ki_tdev == NODEV)
-		PS_ADD("tty",	"%s",	"-1");
-	else
-		PS_ADD("tty",		"%ju",	(uintmax_t)kp.ki_tdev);
+	PS_ADD("tty",		"%d",	tty_nr);
 	PS_ADD("tpgid",		"%d",	kp.ki_tpgid);
 	PS_ADD("flags",		"%u",	0); /* XXX */
 	PS_ADD("minflt",	"%lu",	kp.ki_rusage.ru_minflt);