[PATCH 1/1] Fix: arm: kprobes: optimized kprobes illegal instruction

[Mathieu Desnoyers]

commit e46daee53bb5 "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/342740659.2887.1549307721609.JavaMail.zimbra@xxxxxxxxxxxx
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Reported-by: Robert Berger <Robert.Berger@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Tested-by: Robert Berger <Robert.Berger@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
CC: Robert Berger <Robert.Berger@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
CC: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
CC: William Cohen <wcohen@xxxxxxxxxx>
CC: Laura Abbott <labbott@xxxxxxxxxx>
CC: Kees Cook <keescook@xxxxxxxxxxxx>
CC: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
CC: <stable@xxxxxxxxxxxxxxx> # v4.14+
---
 arch/arm/probes/kprobes/opt-arm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/probes/kprobes/opt-arm.c b/arch/arm/probes/kprobes/opt-arm.c
index 2c118a6ab358..0dc23fc227ed 100644
--- a/arch/arm/probes/kprobes/opt-arm.c
+++ b/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. */
-- 
2.11.0