1 files changed, 116 insertions, 0 deletions

diff --git a/fs/cachefiles/security.c b/fs/cachefiles/security.c
new file mode 100644
index 000000000000..b5808cdb2232
--- /dev/null
+++ b/fs/cachefiles/security.c
@@ -0,0 +1,116 @@
+/* CacheFiles security management
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/fs.h>
+#include <linux/cred.h>
+#include "internal.h"
+
+/*
+ * determine the security context within which we access the cache from within
+ * the kernel
+ */
+int cachefiles_get_security_ID(struct cachefiles_cache *cache)
+{
+        struct cred *new;
+        int ret;
+
+        _enter("{%s}", cache->secctx);
+
+        new = prepare_kernel_cred(current);
+        if (!new) {
+                ret = -ENOMEM;
+                goto error;
+        }
+
+        if (cache->secctx) {
+                ret = set_security_override_from_ctx(new, cache->secctx);
+                if (ret < 0) {
+                        put_cred(new);
+                        printk(KERN_ERR "CacheFiles:"
+                               " Security denies permission to nominate"
+                               " security context: error %d\n",
+                               ret);
+                        goto error;
+                }
+        }
+
+        cache->cache_cred = new;
+        ret = 0;
+error:
+        _leave(" = %d", ret);
+        return ret;
+}
+
+/*
+ * see if mkdir and create can be performed in the root directory
+ */
+static int cachefiles_check_cache_dir(struct cachefiles_cache *cache,
+                                      struct dentry *root)
+{
+        int ret;
+
+        ret = security_inode_mkdir(root->d_inode, root, 0);
+        if (ret < 0) {
+                printk(KERN_ERR "CacheFiles:"
+                       " Security denies permission to make dirs: error %d",
+                       ret);
+                return ret;
+        }
+
+        ret = security_inode_create(root->d_inode, root, 0);
+        if (ret < 0)
+                printk(KERN_ERR "CacheFiles:"
+                       " Security denies permission to create files: error %d",
+                       ret);
+
+        return ret;
+}
+
+/*
+ * check the security details of the on-disk cache
+ * - must be called with security override in force
+ */
+int cachefiles_determine_cache_security(struct cachefiles_cache *cache,
+                                        struct dentry *root,
+                                        const struct cred **_saved_cred)
+{
+        struct cred *new;
+        int ret;
+
+        _enter("");
+
+        /* duplicate the cache creds for COW (the override is currently in
+         * force, so we can use prepare_creds() to do this) */
+        new = prepare_creds();
+        if (!new)
+                return -ENOMEM;
+
+        cachefiles_end_secure(cache, *_saved_cred);
+
+        /* use the cache root dir's security context as the basis with
+         * which create files */
+        ret = set_create_files_as(new, root->d_inode);
+        if (ret < 0) {
+                _leave(" = %d [cfa]", ret);
+                return ret;
+        }
+
+        put_cred(cache->cache_cred);
+        cache->cache_cred = new;
+
+        cachefiles_begin_secure(cache, _saved_cred);
+        ret = cachefiles_check_cache_dir(cache, root);
+
+        if (ret == -EOPNOTSUPP)
+                ret = 0;
+        _leave(" = %d", ret);
+        return ret;
+}