FAILED: patch "[PATCH] signal/arm64: Use force_sig not force_sig_fault for SIGKILL" failed to apply to 5.1-stable tree

The patch below does not apply to the 5.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 82e10af2248d2d09c99834613f1b47d5002dc379 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <[email protected]>
Date: Thu, 16 May 2019 10:55:21 -0500
Subject: [PATCH] signal/arm64: Use force_sig not force_sig_fault for SIGKILL

I don't think this is userspace visible but SIGKILL does not have any si_codes that use the fault member of the siginfo union. Correct this the simple way and call force_sig instead of force_sig_fault when the signal is SIGKILL.

The two know places where synchronous SIGKILL are generated are do_bad_area and fpsimd_save. The call paths to force_sig_fault are:
do_bad_area
arm64_force_sig_fault
force_sig_fault
force_signal_inject
arm64_notify_die
arm64_force_sig_fault
force_sig_fault

Which means correcting this in arm64_force_sig_fault is enough to ensure the arm64 code is not misusing the generic code, which could lead to maintenance problems later.

index ade32046f3fe..e45d5b440fb1 100644
@@ -256,7 +256,10 @@ void arm64_force_sig_fault(int signo, int code, void __user *addr,
 			   const char *str)
 {
 	arm64_show_signal(signo, str);
-	force_sig_fault(signo, code, addr, current);
+	if (signo == SIGKILL)
+		force_sig(SIGKILL, current);
+	else
+		force_sig_fault(signo, code, addr, current);
 }
 
 void arm64_force_sig_mceerr(int code, void __user *addr, short lsb,