[PATCH v2 2/2] tty: check tcsetpgrp p is a process group

[Patrick Donnelly <batrick@batbytes.com>]

This fixes a bug where a process can set the foreground process group to its
pid even if its pid is not a valid pgrp.

Signed-off-by: Patrick Donnelly <batrick@batbytes.com>
---
 drivers/tty/tty_io.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index fbb55db..01b4769 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2579,6 +2579,9 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
 	retval = -ESRCH;
 	if (!pgrp)
 		goto out_unlock;
+	retval = -EINVAL;
+	if (!pid_task(pgrp, PIDTYPE_PGID))
+		goto out_unlock;
 	retval = -EPERM;
 	if (session_of_pgrp(pgrp) != task_session(current))
 		goto out_unlock;
-- 
Patrick Donnelly