NFSv4.2: another fix for listxattr

JIRA: https://issues.redhat.com/browse/RHEL-100709

commit 9acb237
Author: Olga Kornievskaia <okorniev@redhat.com>
Date:   Tue Jul 22 16:56:41 2025 -0400

    NFSv4.2: another fix for listxattr

    Currently, when the server supports NFS4.1 security labels then
    security.selinux label in included twice. Instead, only add it
    when the server doesn't possess security label support.

    Fixes: 243fea1 ("NFSv4.2: fix listxattr to return selinux security label")
    Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
    Link: https://lore.kernel.org/r/20250722205641.79394-1-okorniev@redhat.com
    Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>

Author: Olga Kornievskaia

fs/nfs/nfs4proc.c

@@ -10831,7 +10831,7 @@ const struct nfs4_minor_version_ops *nfs_v4_minor_ops[] = {
 
 static ssize_t nfs4_listxattr(struct dentry *dentry, char *list, size_t size)
 {
-	ssize_t error, error2, error3, error4;
+	ssize_t error, error2, error3, error4 = 0;
 	size_t left = size;
 
 	error = generic_listxattr(dentry, list, left);
@@ -10859,9 +10859,11 @@ static ssize_t nfs4_listxattr(struct dentry *dentry, char *list, size_t size)
 		left -= error3;
 	}
 
-	error4 = security_inode_listsecurity(d_inode(dentry), list, left);
-	if (error4 < 0)
-		return error4;
+	if (!nfs_server_capable(d_inode(dentry), NFS_CAP_SECURITY_LABEL)) {
+		error4 = security_inode_listsecurity(d_inode(dentry), list, left);
+		if (error4 < 0)
+			return error4;
+	}
 
 	error += error2 + error3 + error4;
 	if (size && error > size)