[PATCH v3 2/2] 9p/trans_xen: replace simple_strto* with kstrtouint

[Eric-Terminal <ericterminal@gmail.com>]

From: Yufan Chen <ericterminal@gmail.com>

In xen_9pfs_front_init(), parse the backend version list as comma-separated
tokens with kstrtouint(), keep strict token validation, and explicitly
require protocol version 1 to be present.

This replaces the deprecated simple_strtoul(), improves error reporting
consistency, and avoids partially parsed values in control paths.

Signed-off-by: Yufan Chen <ericterminal@gmail.com>
---
v3:
- Split from mixed series into a dedicated 9p/trans_xen series.
- Refined commit message to focus on 9p changes.
- No functional changes since v2.

 net/9p/trans_xen.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 85b9ebfaa..f9fb2db7a 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -413,23 +413,29 @@ static int xen_9pfs_front_init(struct xenbus_device *dev)
 	int ret, i;
 	struct xenbus_transaction xbt;
 	struct xen_9pfs_front_priv *priv;
-	char *versions, *v;
-	unsigned int max_rings, max_ring_order, len = 0;
+	char *versions, *v, *token;
+	bool version_1 = false;
+	unsigned int max_rings, max_ring_order, len = 0, version;
 
 	versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
 	if (IS_ERR(versions))
 		return PTR_ERR(versions);
-	for (v = versions; *v; v++) {
-		if (simple_strtoul(v, &v, 10) == 1) {
-			v = NULL;
-			break;
+	for (v = versions; (token = strsep(&v, ",")); ) {
+		if (!*token)
+			continue;
+
+		ret = kstrtouint(token, 10, &version);
+		if (ret) {
+			kfree(versions);
+			return ret;
 		}
-	}
-	if (v) {
-		kfree(versions);
-		return -EINVAL;
+		if (version == 1)
+			version_1 = true;
 	}
 	kfree(versions);
+	if (!version_1)
+		return -EINVAL;
+
 	max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
 	if (max_rings < XEN_9PFS_NUM_RINGS)