linux-kernel - [PATCH 4.19 126/293] 9p/xen: Fix end of loop tests for list_for_each

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Message-Id: <20210920163937.570612652@linuxfoundation.org>
Date:   Mon, 20 Sep 2021 18:41:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Harshvardhan Jha <harshvardhan.jha@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Dominique Martinet <asmadeus@...ewreck.org>
Subject: [PATCH 4.19 126/293] 9p/xen: Fix end of loop tests for list_for_each_entry

From: Harshvardhan Jha <harshvardhan.jha@...cle.com>

commit 732b33d0dbf17e9483f0b50385bf606f724f50a2 upstream.

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.

Link: http://lkml.kernel.org/r/20210727000709.225032-1-harshvardhan.jha@oracle.com
Signed-off-by: Harshvardhan Jha <harshvardhan.jha@...cle.com>
Reviewed-by: Stefano Stabellini <sstabellini@...nel.org>
Tested-by: Stefano Stabellini <sstabellini@...nel.org>
Cc: <stable@...r.kernel.org>
Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/9p/trans_xen.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -138,7 +138,7 @@ static bool p9_xen_write_todo(struct xen
 
 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_clie
 			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;