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

[Oleg Nesterov <oleg@tv-sign.ru>]

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>

--- t/drivers/char/n_tty.c~	2007-04-05 12:18:26.000000000 +0400
+++ t/drivers/char/n_tty.c	2007-05-28 10:57:58.000000000 +0400
@@ -1191,6 +1191,7 @@ static int job_control(struct tty_struct
 			    is_current_pgrp_orphaned())
 				return -EIO;
 			kill_pgrp(task_pgrp(current), SIGTTIN, 1);
+			set_thread_flag(TIF_SIGPENDING);
 			return -ERESTARTSYS;
 		}
 	}
--- t/drivers/char/tty_io.c~	2007-04-05 12:18:26.000000000 +0400
+++ t/drivers/char/tty_io.c	2007-05-29 22:15:52.000000000 +0400
@@ -1121,7 +1121,8 @@ int tty_check_change(struct tty_struct *
 		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;
 }
 

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