sysfs: drop kobj_ns_type handling

The way namespace tags are implemented in sysfs is more complicated
than necessary.  As each tag is a pointer value and required to be
non-NULL under a namespace enabled parent, there's no need to record
separately what type each tag is or where namespace is enabled.

If multiple namespace types are needed, which currently aren't, we can
simply compare the tag to a set of allowed tags in the superblock
assuming that the tags, being pointers, won't have the same value
across multiple types.  Also, whether to filter by namespace tag or
not can be trivially determined by whether the node has any tagged
children or not.

This patch rips out kobj_ns_type handling from sysfs.  sysfs no longer
cares whether specific type of namespace is enabled or not.  If a
sysfs_dirent has a non-NULL tag, the parent is marked as needing
namespace filtering and the value is tested against the allowed set of
tags for the superblock (currently only one but increasing this number
isn't difficult) and the sysfs_dirent is ignored if it doesn't match.

This removes most kobject namespace knowledge from sysfs proper which
will enable proper separation and layering of sysfs.  The namespace
sanity checks in fs/sysfs/dir.c are replaced by the new sanity check
in kobject_namespace().  As this is the only place ktype->namespace()
is called for sysfs, this doesn't weaken the sanity check
significantly.  I omitted converting the sanity check in
sysfs_do_create_link_sd().  While the check can be shifted to upper
layer, mistakes there are well contained and should be easily visible
anyway.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 18 deletions

diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 834ec2cdb7a3..8c24bce2f4ae 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -36,7 +36,7 @@ static const struct super_operations sysfs_ops = {
 struct sysfs_dirent sysfs_root = {
         .s_name         = "",
         .s_count        = ATOMIC_INIT(1),
-        .s_flags        = SYSFS_DIR | (KOBJ_NS_TYPE_NONE << SYSFS_NS_TYPE_SHIFT),
+        .s_flags        = SYSFS_DIR,
         .s_mode         = S_IFDIR | S_IRUGO | S_IXUGO,
         .s_ino          = 1,
 };
@@ -77,14 +77,8 @@ static int sysfs_test_super(struct super_block *sb, void *data)
 {
         struct sysfs_super_info *sb_info = sysfs_info(sb);
         struct sysfs_super_info *info = data;
-        enum kobj_ns_type type;
-        int found = 1;
 
-        for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) {
-                if (sb_info->ns[type] != info->ns[type])
-                        found = 0;
-        }
-        return found;
+        return sb_info->ns == info->ns;
 }
 
 static int sysfs_set_super(struct super_block *sb, void *data)
@@ -98,9 +92,7 @@ static int sysfs_set_super(struct super_block *sb, void *data)
 
 static void free_sysfs_super_info(struct sysfs_super_info *info)
 {
-        int type;
-        for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++)
-                kobj_ns_drop(type, info->ns[type]);
+        kobj_ns_drop(KOBJ_NS_TYPE_NET, info->ns);
         kfree(info);
 }
 
@@ -108,7 +100,6 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *data)
 {
         struct sysfs_super_info *info;
-        enum kobj_ns_type type;
         struct super_block *sb;
         int error;
 
@@ -116,18 +107,15 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
                 if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
                         return ERR_PTR(-EPERM);
 
-                for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) {
-                        if (!kobj_ns_current_may_mount(type))
-                                return ERR_PTR(-EPERM);
-                }
+                if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
+                        return ERR_PTR(-EPERM);
         }
 
         info = kzalloc(sizeof(*info), GFP_KERNEL);
         if (!info)
                 return ERR_PTR(-ENOMEM);
 
-        for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++)
-                info->ns[type] = kobj_ns_grab_current(type);
+        info->ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
 
         sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info);
         if (IS_ERR(sb) || sb->s_fs_info != info)