diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2015-11-26 12:58:31 +1100 |
|---|---|---|
| committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2015-11-26 12:58:31 +1100 |
| commit | a871351c143274dbba555a8d9ae44530d77a5884 (patch) | |
| tree | f43d11cd000a4ad945b54aaea881ed11387b48c7 | |
| parent | 60a9beced0b90f14e482a304b5bad005a4b9ff07 (diff) | |
ptrace: make wait_on_bit(JOBCTL_TRAPPING_BIT) in ptrace_attach() killable
ptrace_attach() can hang waiting for STOPPED -> TRACED transition if the
tracee gets frozen in between, change wait_on_bit() to use TASK_KILLABLE.
This doesn't really solve the problem(s) and we probably need to fix the
freezer. In particular, note that this means that pm freezer will fail if
it races attach-to-stopped-task.
And otoh perhaps we can just remove JOBCTL_TRAPPING_BIT altogether, it is
not clear if we really need to hide this transition from debugger, WNOHANG
after PTRACE_ATTACH can fail anyway if it races with SIGCONT.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Roland McGrath <roland@hack.frob.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Pedro Alves <palves@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | kernel/ptrace.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c index b760bae64cf1..aa94aee9d4c9 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -364,8 +364,14 @@ unlock_creds: mutex_unlock(&task->signal->cred_guard_mutex); out: if (!retval) { - wait_on_bit(&task->jobctl, JOBCTL_TRAPPING_BIT, - TASK_UNINTERRUPTIBLE); + /* + * We do not bother to change retval or clear JOBCTL_TRAPPING + * if wait_on_bit() was interrupted by SIGKILL. The tracer will + * not return to user-mode, it will exit and clear this bit in + * __ptrace_unlink() if it wasn't already cleared by the tracee; + * and until then nobody can ptrace this task. + */ + wait_on_bit(&task->jobctl, JOBCTL_TRAPPING_BIT, TASK_KILLABLE); proc_ptrace_connector(task, PTRACE_ATTACH); } |