[PATCH] pid: replace is_orphaned_pgrp with is_current_pgrp_orphaned

Every call to is_orphaned_pgrp passed in process_group(current) which is racy
with respect to another thread changing our process group.  It didn't bite us
because we were dealing with integers and the worse we would get would be a
stale answer.

In switching the checks to use struct pid to be a little more efficient and
prepare the way for pid namespaces this race became apparent.

So I simplified the calls to the more specialized is_current_pgrp_orphaned so
I didn't have to worry about making logic changes to avoid the race.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 3 insertions, 3 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 407b80a..f132349 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -229,12 +229,12 @@ static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignor
 	return ret;	/* (sighing) "Often!" */
 }
 
-int is_orphaned_pgrp(int pgrp)
+int is_current_pgrp_orphaned(void)
 {
 	int retval;
 
 	read_lock(&tasklist_lock);
-	retval = will_become_orphaned_pgrp(find_pid(pgrp), NULL);
+	retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
 	read_unlock(&tasklist_lock);
 
 	return retval;
diff --git a/kernel/signal.c b/kernel/signal.c
index de66def..a9b679e 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1909,7 +1909,7 @@ relock:
 
 				/* signals can be posted during this window */
 
-				if (is_orphaned_pgrp(process_group(current)))
+				if (is_current_pgrp_orphaned())
 					goto relock;
 
 				spin_lock_irq(&current->sighand->siglock);