[PATCH 2/2] 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 | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 401d05e..c20a2fb 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2560,9 +2560,11 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
 {
 	struct pid *pgrp;
 	pid_t pgrp_nr;
-	int retval = tty_check_change(real_tty);
+	int retval;
 	unsigned long flags;
 
+	retval = tty_check_change(real_tty);
+
 	if (retval == -EIO)
 		return -ENOTTY;
 	if (retval)
@@ -2580,6 +2582,10 @@ 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