From: Oleg Nesterov <oleg@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Tested-by: Kyle Huey <me@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/signal.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff -puN kernel/signal.c~protect-the-traced-signal_unkillable-tasks-from-sigkill kernel/signal.c --- a/kernel/signal.c~protect-the-traced-signal_unkillable-tasks-from-sigkill +++ a/kernel/signal.c @@ -94,13 +94,15 @@ static int sig_ignored(struct task_struc 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); } /* _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
