kernel/signal.c: protect the traced SIGNAL_UNKILLABLE tasks from SIGKILL
authorOleg Nesterov <oleg@redhat.com>
Fri, 17 Nov 2017 23:30:01 +0000 (15:30 -0800)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 10 Jan 2018 08:31:20 +0000 (09:31 +0100)
commit2ebd69e8c251597f51768dce320cc10f9b4c8894
tree199ed39f62480e7e4b98d0540fdb4c3edfe56d73
parent22af48be826c4193bba2f11112330aabb2568594
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