[PATCH 4.9 89/93] signal: protect SIGNAL_UNKILLABLE from unintentional clearing.

4.9-stable review patch. If anyone has any objections, please let me know. -- From: Jamie Iles [ Upstream commit 2d39b3cd34e6d323720d4c61bd714f5ae202c022 ] Since commit 00cd5c37afd5 ("ptrace: permit ptracing of /sbin/init") we can now trace init

[PATCH 4.9 89/93] signal: protect SIGNAL_UNKILLABLE from unintentional clearing.

4.9-stable review patch. If anyone has any objections, please let me know. -- From: Jamie Iles [ Upstream commit 2d39b3cd34e6d323720d4c61bd714f5ae202c022 ] Since commit 00cd5c37afd5 ("ptrace: permit ptracing of /sbin/init") we can now trace init processes. init is initially