Commit 628c1bcb authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds

kernel/signal.c: protect the traced SIGNAL_UNKILLABLE tasks from SIGKILL

The comment in sig_ignored() says "Tracers may want to know about even
ignored signals" but SIGKILL can not be reported to debugger and it is
just wrong to return 0 in this case: SIGKILL should only kill the
SIGNAL_UNKILLABLE task if it comes from the parent ns.

Change sig_ignored() to ignore ->ptrace if sig == SIGKILL and rely on
sig_task_ignored().

SISGTOP coming from within the namespace is not really right too but at
least debugger can intercept it, and we can't drop it here because this
will break "gdb -p 1": ptrace_attach() won't work.  Perhaps we will add
another ->ptrace check later, we will see.

Link: http://lkml.kernel.org/r/20171103184206.GB21036@redhat.comSigned-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Tested-by: Kyle Huey's avatarKyle Huey <me@kylehuey.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent eecd7f4f
......@@ -94,13 +94,15 @@ static int sig_ignored(struct task_struct *t, int sig, bool force)
if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
return 0;
if (!sig_task_ignored(t, sig, force))
return 0;
/*
* Tracers may want to know about even ignored signals.
* Tracers may want to know about even ignored signal unless it
* is SIGKILL which can't be reported anyway but can be ignored
* by SIGNAL_UNKILLABLE task.
*/
return !t->ptrace;
if (t->ptrace && sig != SIGKILL)
return 0;
return sig_task_ignored(t, sig, force);
}
/*
......
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