linux-kernel - [PATCH] 9p/xen: Fix end of loop tests for list_for_each

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Date:   Tue, 27 Jul 2021 05:37:10 +0530
From:   Harshvardhan Jha <harshvardhan.jha@...cle.com>
To:     ericvh@...il.com
Cc:     lucho@...kov.net, asmadeus@...ewreck.org, davem@...emloft.net,
        kuba@...nel.org, v9fs-developer@...ts.sourceforge.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Harshvardhan Jha <harshvardhan.jha@...cle.com>
Subject: [PATCH] 9p/xen: Fix end of loop tests for list_for_each_entry

This patch addresses the following problems:
 - priv can never be NULL, so this part of the check is useless
 - if the loop ran through the whole list, priv->client is invalid and
it is more appropriate and sufficient to check for the end of
list_for_each_entry loop condition.

Signed-off-by: Harshvardhan Jha <harshvardhan.jha@...cle.com>
---
 net/9p/trans_xen.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index f4fea28e05da..3ec1a51a6944 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -138,7 +138,7 @@ static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
 
 static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
 {
-	struct xen_9pfs_front_priv *priv = NULL;
+	struct xen_9pfs_front_priv *priv;
 	RING_IDX cons, prod, masked_cons, masked_prod;
 	unsigned long flags;
 	u32 size = p9_req->tc.size;
@@ -151,7 +151,7 @@ static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
 			break;
 	}
 	read_unlock(&xen_9pfs_lock);
-	if (!priv || priv->client != client)
+	if (list_entry_is_head(priv, &xen_9pfs_devs, list))
 		return -EINVAL;
 
 	num = p9_req->tc.tag % priv->num_rings;
-- 
2.32.0