[patch 35/96] copy_process: fix CLONE_PARENT && parent_exec_id interaction

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Oleg Nesterov <oleg@xxxxxxxxxx>

commit 2d5516cbb9daf7d0e342a2e3b0fc6f8c39a81205 upstream.

CLONE_PARENT can fool the ->self_exec_id/parent_exec_id logic. If we
re-use the old parent, we must also re-use ->parent_exec_id to make
sure exit_notify() sees the right ->xxx_exec_id's when the CLONE_PARENT'ed
task exits.

Also, move down the "p->parent_exec_id = p->self_exec_id" thing, to place
two different cases together.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Serge E. Hallyn <serge@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 kernel/fork.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1137,10 +1137,6 @@ static struct task_struct *copy_process(
 #endif
 	clear_all_latency_tracing(p);
 
-	/* Our parent execution domain becomes current domain
-	   These must match for thread signalling to apply */
-	p->parent_exec_id = p->self_exec_id;
-
 	/* ok, now we should be set up.. */
 	p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
 	p->pdeath_signal = 0;
@@ -1178,10 +1174,13 @@ static struct task_struct *copy_process(
 		set_task_cpu(p, smp_processor_id());
 
 	/* CLONE_PARENT re-uses the old parent */
-	if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
+	if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
 		p->real_parent = current->real_parent;
-	else
+		p->parent_exec_id = current->parent_exec_id;
+	} else {
 		p->real_parent = current;
+		p->parent_exec_id = current->self_exec_id;
+	}
 
 	spin_lock(&current->sighand->siglock);
 


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