ARC: mm: fix uninitialised signal code in do_page_fault

[ Upstream commit 121e38e5acdc8e1e4cdb750fcdcc72f94e420968 ]

Commit 15773ae938d8 ("signal/arc: Use force_sig_fault where
appropriate") introduced undefined behaviour by leaving si_code
unitiailized and leaking random kernel values to user space.

Fixes: 15773ae938d8 ("signal/arc: Use force_sig_fault where appropriate")
Signed-off-by: NEugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/arc/mm/fault.c

@@ -66,7 +66,7 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
 	struct vm_area_struct *vma = NULL;
 	struct task_struct *tsk = current;
 	struct mm_struct *mm = tsk->mm;
-	int si_code;
+	int si_code = 0;
 	int ret;
 	vm_fault_t fault;
 	int write = regs->ecr_cause & ECR_C_PROTV_STORE;  /* ST/EX */