2007-11-21 16:00:58

by Oleg Nesterov

Subject: [PATCH -mm 3/3] ptrace_check_attach: remove unneeded ->signal != NULL check

It is not possible to see the PT_PTRACED task without ->signal/sighand under
tasklist_lock, release_task() does ptrace_unlink() first. If the task was
already released before, ptrace_attach() can't succeed and set PT_PTRACED.
Remove this check.

Signed-off-by: Oleg Nesterov <[email protected]>

--- PT/kernel/ptrace.c~3_signal 2007-11-21 16:53:39.000000000 +0300
+++ PT/kernel/ptrace.c 2007-11-21 17:20:24.000000000 +0300
@@ -99,9 +99,12 @@ int ptrace_check_attach(struct task_stru
* be changed by us so it's not changing right after this.
*/
read_lock(&tasklist_lock);
- if ((child->ptrace & PT_PTRACED) && child->parent == current &&
- child->signal != NULL) {
+ if ((child->ptrace & PT_PTRACED) && child->parent == current) {
ret = 0;
+ /*
+ * child->sighand can't be NULL, release_task()
+ * does ptrace_unlink() before __exit_signal().
+ */
spin_lock_irq(&child->sighand->siglock);
if (is_task_stopped(child))
__set_task_state(child, TASK_TRACED);

2007-12-11 01:20:50

by Roland McGrath

Subject: Re: [PATCH -mm 3/3] ptrace_check_attach: remove unneeded ->signal != NULL check

This looks fine to me.

Thanks,
Roland