From: Aristeu Rozanski <arozansk@redhat.com>
Date: Wed, 22 Aug 2007 16:19:55 -0400
Subject: [char] tty: set pending_signal on return -ERESTARTSYS
Message-id: 20070822201955.GC13379@redhat.com
O-Subject: [RHEL5.2 PATCH] tty: set pending_signal() when returning -ERESTARTSYS
Bugzilla: 253873

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=253873

Everytime that ERESTARTSYS is returned pending_signal() must be set to
avoid leaking it to userspace. This patch fixes job_control() and
tty_check_change() to do that.

This patch is a backport of 040b6362d58fe9a344e053546c12bf821f6fce99

Tested by me.

Acked-by: Roland McGrath <roland@redhat.com>
Acked-by: Prarit Bhargava <prarit@redhat.com>
---
 drivers/char/n_tty.c  |    1 +
 drivers/char/tty_io.c |    3 ++-
 include/linux/errno.h |    7 ++++++-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 603b9ad..9f57353 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -1192,6 +1192,7 @@ static int job_control(struct tty_struct *tty, struct file *file)
 			    is_orphaned_pgrp(process_group(current)))
 				return -EIO;
 			kill_pg(process_group(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 e3bab3f..5d2ec17 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1129,7 +1129,8 @@ int tty_check_change(struct tty_struct * tty)
 		return 0;
 	if (is_orphaned_pgrp(process_group(current)))
 		return -EIO;
-	(void) kill_pg(process_group(current), SIGTTOU, 1);
+	kill_pg(process_group(current), SIGTTOU, 1);
+	set_thread_flag(TIF_SIGPENDING);
 	return -ERESTARTSYS;
 }
 
diff --git a/include/linux/errno.h b/include/linux/errno.h
index 504cc19..c630b82 100644
--- a/include/linux/errno.h
+++ b/include/linux/errno.h
@@ -5,7 +5,12 @@
 
 #ifdef __KERNEL__
 
-/* Should never be seen by user programs */
+/*
+ * These should never be seen by user programs.  To return one of ERESTART*
+ * codes, signal_pending() MUST be set.  Note that ptrace can observe these
+ * at syscall exit tracing, but they will never be left for the debugged user
+ * process to see.
+ */
 #define ERESTARTSYS	512
 #define ERESTARTNOINTR	513
 #define ERESTARTNOHAND	514	/* restart if no handler.. */
-- 
1.5.3.5.645.gbb47