From dd83c161fbcc5d8be637ab159c0de015cbff5ba4 Mon Sep 17 00:00:00 2001
From: zhongjiang <zhongjiang@huawei.com>
Date: Mon, 10 Jul 2017 15:53:01 -0700
Subject: [PATCH] kernel/exit.c: avoid undefined behaviour when calling wait4()
Git-commit: dd83c161fbcc5d8be637ab159c0de015cbff5ba4
Patch-mainline: v4.13-rc1
References: bnc#1089608, CVE-2018-10087

wait4(-2147483648, 0x20, 0, 0xdd0000) triggers:
Ubsan: Undefined behaviour in kernel/exit.c:1651:9

The related calltrace is as follows:

  negation of -2147483648 cannot be represented in type 'int':
  CPU: 9 PID: 16482 Comm: zj Tainted: G    B          ---- -------   3.10.0-327.53.58.71.x86_64+ #66
  Hardware name: Huawei Technologies Co., Ltd. Tecal RH2285          /BC11BTSA              , BIOS CTSAV036 04/27/2011
  Call Trace:
    dump_stack+0x19/0x1b
    ubsan_epilogue+0xd/0x50
    __ubsan_handle_negate_overflow+0x109/0x14e
    SyS_wait4+0x1cb/0x1e0
    system_call_fastpath+0x16/0x1b

Exclude the overflow to avoid the UBSAN warning.

Link: http://lkml.kernel.org/r/1497264618-20212-1-git-send-email-zhongjiang@huawei.com
Signed-off-by: zhongjiang <zhongjiang@huawei.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>

---
 kernel/exit.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/exit.c b/kernel/exit.c
index 608c9775a37b..c5548faa9f37 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1639,6 +1639,10 @@ long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
 			__WNOTHREAD|__WCLONE|__WALL))
 		return -EINVAL;
 
+	/* -INT_MIN is not defined */
+	if (upid == INT_MIN)
+		return -ESRCH;
+
 	if (upid == -1)
 		type = PIDTYPE_MAX;
 	else if (upid < 0) {
-- 
1.8.5.6