Eric Lee / smarc-ti-linux-kernel

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Commit 8a88951b5878dc475dcd841cefc767e36397d14e

Authored by Oleg Nesterov
Committed by Linus Torvalds
1 parent 50b8d25748
Exists in master and in 20 other branches dlt-processor-sdk-linux-03.00.00.04, newt-ti-linux-3.12.y, processor-sdk-linux-01.00.00, processor-sdk-linux-02.00.01, smarc-ti-linux-3.12.10, smarc-ti-linux-3.12.y, smarc-ti-linux-3.14.y, smarc-ti-linux-3.15.y, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04, ti-linux-3.12.y, ti-linux-3.14.y, ti-linux-3.15.y, ti-lsk-linux-4.1.y

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>

Showing 2 changed files with 12 additions and 3 deletions Side-by-side Diff

... ... @@ -96,8 +96,19 @@
96 96 */
97 97 if (!(child->flags & PF_EXITING) &&
98 98 (child->signal->flags & SIGNAL_STOP_STOPPED ||
99   - child->signal->group_stop_count))
  99 + child->signal->group_stop_count)) {
100 100 child->jobctl |= JOBCTL_STOP_PENDING;
  101 +
  102 + /*
  103 + * This is only possible if this thread was cloned by the
  104 + * traced task running in the stopped group, set the signal
  105 + * for the future reports.
  106 + * FIXME: we should change ptrace_init_task() to handle this
  107 + * case.
  108 + */
  109 + if (!(child->jobctl & JOBCTL_STOP_SIGMASK))
  110 + child->jobctl |= SIGSTOP;
  111 + }
101 112  
102 113 /*
103 114 * If transition to TASK_STOPPED is pending or in TASK_TRACED, kick
... ... @@ -1994,8 +1994,6 @@
1994 1994 */
1995 1995 if (!(sig->flags & SIGNAL_STOP_STOPPED))
1996 1996 sig->group_exit_code = signr;
1997   - else
1998   - WARN_ON_ONCE(!current->ptrace);
1999 1997  
2000 1998 sig->group_stop_count = 0;
2001 1999