Messages in this thread Patch in this message | | | Date | Fri, 3 Feb 2023 15:31:11 +0100 | From | Peter Zijlstra <> | Subject | Re: [syzbot] WARNING: locking bug in umh_complete |
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On Fri, Feb 03, 2023 at 09:59:51PM +0900, Tetsuo Handa wrote: > On 2023/02/03 21:30, Peter Zijlstra wrote: > >> I think the right fix is to: > >> > >> state &= ~TASK_KILLABLE; > > > > state &= ~__TASK_WAKEKILL; > > > > we don't want to mask out UNINTERUPTIBLE, that would be bad. > > This code was made killable as a solution for CVE-2012-4398. > Although OOM reaper is available today, making back to unkillable is not smart.
Yes, I meant something like so.
diff --git a/kernel/umh.c b/kernel/umh.c index 850631518665..0e69e1e4b6fe 100644 --- a/kernel/umh.c +++ b/kernel/umh.c @@ -438,21 +438,24 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait) if (wait == UMH_NO_WAIT) /* task has freed sub_info */ goto unlock; - if (wait & UMH_KILLABLE) - state |= TASK_KILLABLE; - - if (wait & UMH_FREEZABLE) + if (wait & UMH_FREEZABLE) { state |= TASK_FREEZABLE; - retval = wait_for_completion_state(&done, state); - if (!retval) - goto wait_done; - if (wait & UMH_KILLABLE) { + retval = wait_for_completion_state(&done, state | TASK_KILLABLE); + if (!retval) + goto wait_done; + /* umh_complete() will see NULL and free sub_info */ if (xchg(&sub_info->complete, NULL)) goto unlock; + + /* + * fallthrough; in case of -ERESTARTSYS now do uninterruptible + * wait_for_completion(). + */ } + wait_for_completion_state(&done, state); wait_done: retval = sub_info->retval;
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