From 1d50109a693c22ea6ac80991ae492ea9e1423a23 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trondmy@gmail.com>
Date: Thu, 29 Apr 2021 14:56:21 +0800
Subject: [PATCH] SUNRPC: Don't allow compiler optimisation of
 svc_xprt_release_slot()

mainline inclusion
from mainline-5.1-rc1
commit 1602a7b7d33741d0490682e620bb29e96ad684d7
category: bugfix
bugzilla: 51818
CVE: NA

-------------------------------------------------
Use READ_ONCE() to tell the compiler to not optimse away the read of
xprt->xpt_flags in svc_xprt_release_slot().

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Reviewed-by: Yue Haibing <yuehaibing@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 net/sunrpc/svc_xprt.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 0f89fc6c92e2..0ab649e02861 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -373,9 +373,13 @@ static void svc_xprt_release_slot(struct svc_rqst *rqstp)
 
 static bool svc_xprt_has_something_to_do(struct svc_xprt *xprt)
 {
-	if (xprt->xpt_flags & ((1<<XPT_CONN)|(1<<XPT_CLOSE)))
+	unsigned long xpt_flags;
+
+	xpt_flags = READ_ONCE(xprt->xpt_flags);
+
+	if (xpt_flags & (BIT(XPT_CONN) | BIT(XPT_CLOSE)))
 		return true;
-	if (xprt->xpt_flags & ((1<<XPT_DATA)|(1<<XPT_DEFERRED))) {
+	if (xpt_flags & (BIT(XPT_DATA) | BIT(XPT_DEFERRED))) {
 		if (xprt->xpt_ops->xpo_has_wspace(xprt) &&
 		    svc_xprt_slots_in_range(xprt))
 			return true;
-- 
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