netdev - [PATCH 1/2] 9p/xen: fix version parsing

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Message-Id: <20230130113036.7087-2-jgross@suse.com>
Date:   Mon, 30 Jan 2023 12:30:35 +0100
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, v9fs-developer@...ts.sourceforge.net,
        netdev@...r.kernel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Eric Van Hensbergen <ericvh@...il.com>,
        Latchesar Ionkov <lucho@...kov.net>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Christian Schoenebeck <linux_oss@...debyte.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH 1/2] 9p/xen: fix version parsing

When connecting the Xen 9pfs frontend to the backend, the "versions"
Xenstore entry written by the backend is parsed in a wrong way.

The "versions" entry is defined to contain the versions supported by
the backend separated by commas (e.g. "1,2"). Today only version "1"
is defined. Unfortunately the frontend doesn't look for "1" being
listed in the entry, but it is expecting the entry to have the value
"1".

This will result in failure as soon as the backend will support e.g.
versions "1" and "2".

Fix that by scanning the entry correctly.

Fixes: 71ebd71921e4 ("xen/9pfs: connect to the backend")
Signed-off-by: Juergen Gross <jgross@...e.com>
---
 net/9p/trans_xen.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 82c7005ede65..ad2947a3b376 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -378,13 +378,19 @@ static int xen_9pfs_front_probe(struct xenbus_device *dev,
 	int ret, i;
 	struct xenbus_transaction xbt;
 	struct xen_9pfs_front_priv *priv = NULL;
-	char *versions;
+	char *versions, *v;
 	unsigned int max_rings, max_ring_order, len = 0;
 
 	versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
 	if (IS_ERR(versions))
 		return PTR_ERR(versions);
-	if (strcmp(versions, "1")) {
+	for (v = versions; *v; v++) {
+		if (simple_strtoul(v, &v, 10) == 1) {
+			v = NULL;
+			break;
+		}
+	}
+	if (v) {
 		kfree(versions);
 		return -EINVAL;
 	}
-- 
2.35.3