The patch titled
ptrace_detach: the wrong wakeup breaks the ERESTARTxxx logic
has been added to the -mm tree. Its filename is
ptrace_detach-the-wrong-wakeup-breaks-the-erestartxxx-logic.patch
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------------------------------------------------------
Subject: ptrace_detach: the wrong wakeup breaks the ERESTARTxxx logic
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Another ancient bug. Consider this trivial test-case,
int main(void)
{
int pid = fork();
if (pid) {
ptrace(PTRACE_ATTACH, pid, NULL, NULL);
wait(NULL);
ptrace(PTRACE_DETACH, pid, NULL, NULL);
} else {
pause();
printf("WE HAVE A KERNEL BUG!!!\n");
}
return 0;
}
the child must not "escape" for sys_pause(), but it can and this was seen
in practice.
This is because ptrace_detach does:
if (!child->exit_state)
wake_up_process(child);
this wakeup can happen after this child has already restarted sys_pause(),
because it gets another wakeup from ptrace_untrace().
With or without this patch, perhaps sys_pause() needs a fix. But this
wakeup also breaks the SIGNAL_STOP_STOPPED logic in ptrace_untrace().
Remove this wakeup. The caller saw this task in TASK_TRACED state, and
unless it was SIGKILL'ed in between __ptrace_unlink()->ptrace_untrace()
should handle this case correctly. If it was SIGKILL'ed, we don't need to
wakup the dying tracee too.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Jerome Marchand <jmarchan@xxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/ptrace.c | 4 ----
1 file changed, 4 deletions(-)
diff -puN kernel/ptrace.c~ptrace_detach-the-wrong-wakeup-breaks-the-erestartxxx-logic kernel/ptrace.c
--- a/kernel/ptrace.c~ptrace_detach-the-wrong-wakeup-breaks-the-erestartxxx-logic
+++ a/kernel/ptrace.c
@@ -301,11 +301,7 @@ int ptrace_detach(struct task_struct *ch
*/
if (child->ptrace) {
child->exit_code = data;
-
dead = __ptrace_detach(current, child);
-
- if (!child->exit_state)
- wake_up_process(child);
}
write_unlock_irq(&tasklist_lock);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
linux-next.patch
pipe_rdwr_fasync-fix-the-error-handling-to-prevent-the-leak-crash.patch
get_mm_hiwater_xxx-trivial-s-define-inline.patch
getrusage-fill-ru_maxrss-value.patch
do_wait-fix-waiting-for-the-group-stop-with-the-dead-leader.patch
ptrace-kill-__ptrace_detach-fix-exit_state-check.patch
ptrace-simplify-ptrace_exit-ignoring_children-path.patch
ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix.patch
ptrace-reintroduce-__ptrace_detach-as-a-callee-of-ptrace_exit.patch
ptrace-reintroduce-__ptrace_detach-as-a-callee-of-ptrace_exit-fix.patch
ptrace-fix-possible-zombie-leak-on-ptrace_detach.patch
reparent_thread-dont-call-kill_orphaned_pgrp-if-task_detached.patch
reparent_thread-fix-the-is-it-traced-check.patch
reparent_thread-fix-a-zombie-leak-if-sbin-init-ignores-sigchld.patch
forget_original_parent-split-out-the-un-ptrace-part.patch
forget_original_parent-do-not-abuse-child-ptrace_entry.patch
forget_original_parent-do-not-abuse-child-ptrace_entry-fix.patch
move-exit_ptrace-from-forget_original_parent-to-do_exit.patch
reparent-untrace-do-nothing-if-no-childs-tracees.patch
tracehook_notify_death-use-task_detached-helper.patch
ptrace_detach-the-wrong-wakeup-breaks-the-erestartxxx-logic.patch
ptrace_untrace-fix-the-signal_stop_stopped-check.patch
workqueue-avoid-recursion-in-run_workqueue.patch
kthreads-move-sched-realeted-initialization-from-kthreadd-context.patch
kthreads-simplify-the-startup-synchronization.patch
kthreads-rework-kthread_stop.patch
kthreads-simplify-migration_thread-exit-path.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu-fix.patch
pids-improve-get_task_pid-to-fix-the-unsafe-sys_wait4-task_pgrp.patch
pids-refactor-vnr-nr_ns-helpers-to-make-them-safe.patch
pids-kill-now-unused-signal_struct-__pgrp-__session-and-friends.patch
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