[PATCH] tty: fix leakage of -ERESTARTSYS to userland

Spotted by Satoru Takeuchi.

kill_pgrp(task_pgrp(current)) sends the signal to the current's thread
group, but can choose any sub-thread as a target for signal_wake_up().
This means that job_control() and tty_check_change() may return
-ERESTARTSYS without signal_pending().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 6ac3ca4c723c2c660c5d084b9c7834035767fbb5..5a6c649bc993316c4d8282a5f793dc2d182934b0 100644 (file)
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -1191,6 +1191,7 @@ static int job_control(struct tty_struct *tty, struct file *file)
                            is_current_pgrp_orphaned())
                                return -EIO;
                        kill_pgrp(task_pgrp(current), SIGTTIN, 1);
+                       set_thread_flag(TIF_SIGPENDING);
                        return -ERESTARTSYS;
                }
        }

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 7a32df59490750775b6df3b718e0b33be2ee8514..2000120f9ecc8033aefdcf1c9b68a71c77ec8149 100644 (file)
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1121,7 +1121,8 @@ int tty_check_change(struct tty_struct * tty)
                return 0;
        if (is_current_pgrp_orphaned())
                return -EIO;
-       (void) kill_pgrp(task_pgrp(current), SIGTTOU, 1);
+       kill_pgrp(task_pgrp(current), SIGTTOU, 1);
+       set_thread_flag(TIF_SIGPENDING);
        return -ERESTARTSYS;
 }