ptrace: fix possible zombie leak on PTRACE_DETACH
When ptrace_detach() takes tasklist, the tracee can be SIGKILL'ed. If it
has already passed exit_notify() we can leak a zombie, because a) ptracing
disables the auto-reaping logic, and b) ->real_parent was not notified
about the child's death.
ptrace_detach() should follow the ptrace_exit's logic, change the code
accordingly.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Tested-by: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index f62a568..ee553b6 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -237,6 +237,8 @@
int ptrace_detach(struct task_struct *child, unsigned int data)
{
+ int dead = 0;
+
if (!valid_signal(data))
return -EIO;
@@ -244,18 +246,21 @@
ptrace_disable(child);
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
- /* protect against de_thread()->release_task() */
write_lock_irq(&tasklist_lock);
+ /* protect against de_thread()->release_task() */
if (child->ptrace) {
child->exit_code = data;
- __ptrace_unlink(child);
+ dead = __ptrace_detach(current, child);
if (!child->exit_state)
wake_up_process(child);
}
write_unlock_irq(&tasklist_lock);
+ if (unlikely(dead))
+ release_task(child);
+
return 0;
}