From: Oleg Nesterov Date: Fri, 17 Nov 2017 23:30:01 +0000 (-0800) Subject: kernel/signal.c: protect the traced SIGNAL_UNKILLABLE tasks from SIGKILL X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=be95f1308f794861877af032bbb5b6ea48ca66a5;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git 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 Tested-by: Kyle Huey Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/signal.c b/kernel/signal.c index 5d50ea899b6d..fc666bfd411a 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -88,13 +88,15 @@ 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); } /*