[PATCH 4.9 10/21] kernel/signal.c: protect the SIGNAL_UNKILLABLE tasks from !sig_kernel_only() signals

From: Greg Kroah-Hartman
Date: Mon Jan 08 2018 - 08:02:39 EST


4.9-stable review patch. If anyone has any objections, please let me know.

------------------

From: Oleg Nesterov <oleg@xxxxxxxxxx>

commit ac25385089f673560867eb5179228a44ade0cfc1 upstream.

Change sig_task_ignored() to drop the SIG_DFL && !sig_kernel_only()
signals even if force == T. This simplifies the next change and this
matches the same check in get_signal() which will drop these signals
anyway.

Link: http://lkml.kernel.org/r/20171103184227.GC21036@xxxxxxxxxx
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Tested-by: Kyle Huey <me@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
kernel/signal.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -72,7 +72,7 @@ static int sig_task_ignored(struct task_
handler = sig_handler(t, sig);

if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
- handler == SIG_DFL && !force)
+ handler == SIG_DFL && !(force && sig_kernel_only(sig)))
return 1;

return sig_handler_ignored(handler, sig);