Messages in this thread Patch in this message | | | Date | Thu, 6 Dec 2018 12:20:59 -0700 | From | Tycho Andersen <> | Subject | Re: siginfo pid not populated from ptrace? |
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On Thu, Dec 06, 2018 at 10:48:39AM -0800, Linus Torvalds wrote: > On Thu, Dec 6, 2018 at 6:40 AM Eric W. Biederman <ebiederm@xmission.com> wrote: > > > > We have in the past had ptrace users that weren't just about debugging > > so I don't know that it is fair to just dismiss it as debugging > > infrastructure. > > Absolutely. > > Some uses are more than just debug. People occasionally use ptrace > because it's the only way to do what they want, so you'll find people > who do it for sandboxing, for example. It's not necessarily designed > for that, or particularly fast or well-suited for it, but I've > definitely seen it used that way. > > So I don't think the behavioral test breakage like this is necessarily > a huge deal, and until some "real use" actually shows that it cares it > might be something we dismiss as "just test", but it very much has the > potential to hit real uses. > > The fact that a behavioral test broke is definitely interesting. > > And maybe some of the siginfo allocations could depend on whether the > signal is actually ever caught or not. > > For example, a terminal signal (or one that is ignored) might not need > siginfo. But if the process is ptraced, maybe that terminal signal > isn't actually terminal? So we might have situations where we want to > simply check "is the signal target being ptraced"..
Yes, something like this, I suppose? It works for me.
Tycho
From 3bcaadd56ebb532ab4d481556fcc0826d65efc43 Mon Sep 17 00:00:00 2001 From: Tycho Andersen <tycho@tycho.ws> Date: Thu, 6 Dec 2018 12:15:22 -0700 Subject: [PATCH] signal: allocate siginfo when a traced task gets SIGSTOP
Tracers can view SIGSTOP:
https://lore.kernel.org/lkml/87zhtthkuy.fsf@xmission.com/T/#u
so let's allocate a siginfo for SIGSTOP when a task is traced.
Signed-off-by: Tycho Andersen <tycho@tycho.ws> --- kernel/signal.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c index 9a32bc2088c9..ab4ba00119f4 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1056,11 +1056,14 @@ static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struc goto ret; result = TRACE_SIGNAL_DELIVERED; + /* - * Skip useless siginfo allocation for SIGKILL SIGSTOP, - * and kernel threads. + * Skip useless siginfo allocation for SIGKILL and kernel threads. + * SIGSTOP is visible to tracers, so only skip allocation when the task + * is not traced. */ - if (sig_kernel_only(sig) || (t->flags & PF_KTHREAD)) + if ((sig == SIGKILL) || (!task_is_traced(t) && sig == SIGSTOP) || + (t->flags & PF_KTHREAD)) goto out_set; /* -- 2.19.1
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