| Date | Mon, 2 May 2022 16:37:51 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v2 06/12] ptrace: Reimplement PTRACE_KILL by always sending SIGKILL |
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On 04/29, Eric W. Biederman wrote: > > Call send_sig_info in PTRACE_KILL instead of ptrace_resume. Calling > ptrace_resume is not safe to call if the task has not been stopped > with ptrace_freeze_traced.
Oh, I was never, never able to understand why do we have PTRACE_KILL and what should it actually do.
I suggested many times to simply remove it but OK, we probably can't do this.
> --- a/kernel/ptrace.c > +++ b/kernel/ptrace.c > @@ -1238,7 +1238,7 @@ int ptrace_request(struct task_struct *child, long request, > case PTRACE_KILL: > if (child->exit_state) /* already dead */ > return 0; > - return ptrace_resume(child, request, SIGKILL); > + return send_sig_info(SIGKILL, SEND_SIG_NOINFO, child);
Note that currently ptrace(PTRACE_KILL) can never fail (yes, yes, it is unsafe), but send_sig_info() can. If we do not remove PTRACE_KILL, then I'd suggest
case PTRACE_KILL: if (!child->exit_state) send_sig_info(SIGKILL); return 0;
to make this change a bit more compatible.
Also, please remove the note about PTRACE_KILL in set_task_blockstep().
Oleg.
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