ARM: 8834/1: Fix: kprobes: optimized kprobes illegal instruction

commit e46daee ("ARM: 8806/1: kprobes: Fix false positive with
FORTIFY_SOURCE") introduced a regression in optimized kprobes. It
triggers "invalid instruction" oopses when using kprobes instrumentation
through lttng and perf. This commit was introduced in kernel v4.20, and
has been backported to stable kernels 4.19 and 4.14.

This crash was also reported by Hongzhi Song on the redhat bugzilla
where the patch was originally introduced.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1639397
Link: https://bugs.lttng.org/issues/1174
Link: https://lore.kernel.org/lkml/[email protected]

Fixes: e46daee ("ARM: 8806/1: kprobes: Fix false positive with FORTIFY_SOURCE")
Signed-off-by: Mathieu Desnoyers <[email protected]>
Reported-by: Robert Berger <[email protected]>
Tested-by: Robert Berger <[email protected]>
Acked-by: Kees Cook <[email protected]>
Cc: Robert Berger <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: William Cohen <[email protected]>
Cc: Laura Abbott <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: <[email protected]> # v4.14+
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Russell King <[email protected]>

arch/arm/probes/kprobes/opt-arm.c

@@ -247,7 +247,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *or
 	}
 
 	/* Copy arch-dep-instance from template. */
-	memcpy(code, (unsigned char *)optprobe_template_entry,
+	memcpy(code, (unsigned long *)&optprobe_template_entry,
 			TMPL_END_IDX * sizeof(kprobe_opcode_t));
 
 	/* Adjust buffer according to instruction. */