diff options
authorOleg Nesterov <oleg@redhat.com>2012-01-04 17:29:20 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2012-01-04 15:01:59 -0800
commit8a88951b5878dc475dcd841cefc767e36397d14e (patch)
parent50b8d257486a45cba7b65ca978986ed216bbcc10 (diff)
ptrace: ensure JOBCTL_STOP_SIGMASK is not zero after detach
This is the temporary simple fix for 3.2, we need more changes in this area. 1. do_signal_stop() assumes that the running untraced thread in the stopped thread group is not possible. This was our goal but it is not yet achieved: a stopped-but-resumed tracee can clone the running thread which can initiate another group-stop. Remove WARN_ON_ONCE(!current->ptrace). 2. A new thread always starts with ->jobctl = 0. If it is auto-attached and this group is stopped, __ptrace_unlink() sets JOBCTL_STOP_PENDING but JOBCTL_STOP_SIGMASK part is zero, this triggers WANR_ON(!signr) in do_jobctl_trap() if another debugger attaches. Change __ptrace_unlink() to set the artificial SIGSTOP for report. Alternatively we could change ptrace_init_task() to copy signr from current, but this means we can copy it for no reason and hide the possible similar problems. Acked-by: Tejun Heo <tj@kernel.org> Cc: <stable@kernel.org> [3.1] Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2 files changed, 12 insertions, 3 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 24d04477b25..78ab24a7b0e 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -96,9 +96,20 @@ void __ptrace_unlink(struct task_struct *child)
if (!(child->flags & PF_EXITING) &&
(child->signal->flags & SIGNAL_STOP_STOPPED ||
- child->signal->group_stop_count))
+ child->signal->group_stop_count)) {
child->jobctl |= JOBCTL_STOP_PENDING;
+ /*
+ * This is only possible if this thread was cloned by the
+ * traced task running in the stopped group, set the signal
+ * for the future reports.
+ * FIXME: we should change ptrace_init_task() to handle this
+ * case.
+ */
+ if (!(child->jobctl & JOBCTL_STOP_SIGMASK))
+ child->jobctl |= SIGSTOP;
+ }
* If transition to TASK_STOPPED is pending or in TASK_TRACED, kick
* @child in the butt. Note that @resume should be used iff @child
diff --git a/kernel/signal.c b/kernel/signal.c
index b3f78d09a10..206551563cc 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1994,8 +1994,6 @@ static bool do_signal_stop(int signr)
if (!(sig->flags & SIGNAL_STOP_STOPPED))
sig->group_exit_code = signr;
- else
- WARN_ON_ONCE(!current->ptrace);
sig->group_stop_count = 0;