From 2ebd69e8c251597f51768dce320cc10f9b4c8894 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov <oleg@redhat.com> Date: Fri, 17 Nov 2017 15:30:01 -0800 Subject: [PATCH] kernel/signal.c: protect the traced SIGNAL_UNKILLABLE tasks from SIGKILL commit 628c1bcba204052d19b686b5bac149a644cdb72e upstream. 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.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Tested-by: Kyle Huey <me@kylehuey.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- kernel/signal.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index 8dcd8825b2ded..7339d73718859 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -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); } /* -- GitLab