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Message-Id: <20200408152151.5780-7-christian.brauner@ubuntu.com>
Date: Wed, 8 Apr 2020 17:21:49 +0200
From: Christian Brauner <christian.brauner@...ntu.com>
To: Jens Axboe <axboe@...nel.dk>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
linux-api@...r.kernel.org
Cc: Jonathan Corbet <corbet@....net>, Serge Hallyn <serge@...lyn.com>,
"Rafael J. Wysocki" <rafael@...nel.org>, Tejun Heo <tj@...nel.org>,
"David S. Miller" <davem@...emloft.net>,
Christian Brauner <christian.brauner@...ntu.com>,
Saravana Kannan <saravanak@...gle.com>,
Jan Kara <jack@...e.cz>, David Howells <dhowells@...hat.com>,
Seth Forshee <seth.forshee@...onical.com>,
David Rheinsberg <david.rheinsberg@...il.com>,
Tom Gundersen <teg@...m.no>,
Christian Kellner <ckellner@...hat.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Stéphane Graber <stgraber@...ntu.com>,
linux-doc@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH 6/8] genhd: add minimal namespace infrastructure
This lets the block_class properly support loopfs device by introducing
the minimal infrastructure needed to support different sysfs views for
devices belonging to the block_class. This is similar to how network
devices work. Note, that nothing changes with this patch since
all block_class devices are tagged explicitly with init_user_ns whereas
they were tagged implicitly with init_user_ns before. No code is added
if CONFIG_BLK_DEV_LOOPFS is not set.
Cc: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>
---
block/genhd.c | 79 +++++++++++++++++++++++++++++++++++++
fs/kernfs/kernfs-internal.h | 3 ++
fs/sysfs/mount.c | 4 ++
include/linux/genhd.h | 3 ++
include/linux/kobject_ns.h | 1 +
5 files changed, 90 insertions(+)
diff --git a/block/genhd.c b/block/genhd.c
index 9c2e13ce0d19..a6d51d9a94f6 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1127,11 +1127,81 @@ static struct kobject *base_probe(dev_t devt, int *partno, void *data)
return NULL;
}
+#ifdef CONFIG_BLK_DEV_LOOPFS
+static void *user_grab_current_ns(void)
+{
+ struct user_namespace *ns = current_user_ns();
+ return get_user_ns(ns);
+}
+
+static const void *user_initial_ns(void)
+{
+ return &init_user_ns;
+}
+
+static void user_put_ns(void *p)
+{
+ struct user_namespace *ns = p;
+ put_user_ns(ns);
+}
+
+static bool user_current_may_mount(void)
+{
+ return ns_capable(current_user_ns(), CAP_SYS_ADMIN);
+}
+
+const struct kobj_ns_type_operations user_ns_type_operations = {
+ .type = KOBJ_NS_TYPE_USER,
+ .current_may_mount = user_current_may_mount,
+ .grab_current_ns = user_grab_current_ns,
+ .initial_ns = user_initial_ns,
+ .drop_ns = user_put_ns,
+};
+
+static const void *block_class_user_namespace(struct device *dev)
+{
+ struct gendisk *disk;
+
+ if (dev->type == &part_type)
+ disk = part_to_disk(dev_to_part(dev));
+ else
+ disk = dev_to_disk(dev);
+
+ return disk->user_ns;
+}
+
+static void block_class_get_ownership(struct device *dev, kuid_t *uid, kgid_t *gid)
+{
+ struct gendisk *disk;
+ struct user_namespace *ns;
+
+ if (dev->type == &part_type)
+ disk = part_to_disk(dev_to_part(dev));
+ else
+ disk = dev_to_disk(dev);
+
+ ns = disk->user_ns;
+ if (ns && ns != &init_user_ns) {
+ kuid_t ns_root_uid = make_kuid(ns, 0);
+ kgid_t ns_root_gid = make_kgid(ns, 0);
+
+ if (uid_valid(ns_root_uid))
+ *uid = ns_root_uid;
+
+ if (gid_valid(ns_root_gid))
+ *gid = ns_root_gid;
+ }
+}
+#endif /* CONFIG_BLK_DEV_LOOPFS */
+
static int __init genhd_device_init(void)
{
int error;
block_class.dev_kobj = sysfs_dev_block_kobj;
+#ifdef CONFIG_BLK_DEV_LOOPFS
+ kobj_ns_type_register(&user_ns_type_operations);
+#endif
error = class_register(&block_class);
if (unlikely(error))
return error;
@@ -1369,8 +1439,14 @@ static void disk_release(struct device *dev)
blk_put_queue(disk->queue);
kfree(disk);
}
+
struct class block_class = {
.name = "block",
+#ifdef CONFIG_BLK_DEV_LOOPFS
+ .ns_type = &user_ns_type_operations,
+ .namespace = block_class_user_namespace,
+ .get_ownership = block_class_get_ownership,
+#endif
};
static char *block_devnode(struct device *dev, umode_t *mode,
@@ -1550,6 +1626,9 @@ struct gendisk *__alloc_disk_node(int minors, int node_id)
disk_to_dev(disk)->class = &block_class;
disk_to_dev(disk)->type = &disk_type;
device_initialize(disk_to_dev(disk));
+#ifdef CONFIG_BLK_DEV_LOOPFS
+ disk->user_ns = &init_user_ns;
+#endif
}
return disk;
}
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index 4ba7b36103de..699b7b67f9e0 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -79,12 +79,15 @@ static inline struct kernfs_node *kernfs_dentry_node(struct dentry *dentry)
}
extern struct net init_net;
+extern struct user_namespace init_user_ns;
static inline const void *kernfs_init_ns(enum kobj_ns_type ns_type)
{
switch (ns_type) {
case KOBJ_NS_TYPE_NET:
return &init_net;
+ case KOBJ_NS_TYPE_USER:
+ return &init_user_ns;
default:
pr_debug("Unsupported namespace type %d for kernfs\n", ns_type);
}
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 5e2ec88a709e..99b82a0ae7ea 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -43,6 +43,8 @@ static void sysfs_fs_context_free(struct fs_context *fc)
if (kfc->ns_tag[KOBJ_NS_TYPE_NET])
kobj_ns_drop(KOBJ_NS_TYPE_NET, kfc->ns_tag[KOBJ_NS_TYPE_NET]);
+ if (kfc->ns_tag[KOBJ_NS_TYPE_USER])
+ kobj_ns_drop(KOBJ_NS_TYPE_USER, kfc->ns_tag[KOBJ_NS_TYPE_USER]);
kernfs_free_fs_context(fc);
kfree(kfc);
}
@@ -67,6 +69,7 @@ static int sysfs_init_fs_context(struct fs_context *fc)
return -ENOMEM;
kfc->ns_tag[KOBJ_NS_TYPE_NET] = netns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+ kfc->ns_tag[KOBJ_NS_TYPE_USER] = kobj_ns_grab_current(KOBJ_NS_TYPE_USER);
kfc->root = sysfs_root;
kfc->magic = SYSFS_MAGIC;
fc->fs_private = kfc;
@@ -85,6 +88,7 @@ static void sysfs_kill_sb(struct super_block *sb)
kernfs_kill_sb(sb);
kobj_ns_drop(KOBJ_NS_TYPE_NET, ns[KOBJ_NS_TYPE_NET]);
+ kobj_ns_drop(KOBJ_NS_TYPE_USER, ns[KOBJ_NS_TYPE_USER]);
}
static struct file_system_type sysfs_fs_type = {
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 07dc91835b98..e5cf5caea345 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -219,6 +219,9 @@ struct gendisk {
int node_id;
struct badblocks *bb;
struct lockdep_map lockdep_map;
+#ifdef CONFIG_BLK_DEV_LOOPFS
+ struct user_namespace *user_ns;
+#endif
};
static inline struct gendisk *part_to_disk(struct hd_struct *part)
diff --git a/include/linux/kobject_ns.h b/include/linux/kobject_ns.h
index 216f9112ee1d..a9c45bcce235 100644
--- a/include/linux/kobject_ns.h
+++ b/include/linux/kobject_ns.h
@@ -26,6 +26,7 @@ struct kobject;
enum kobj_ns_type {
KOBJ_NS_TYPE_NONE = 0,
KOBJ_NS_TYPE_NET,
+ KOBJ_NS_TYPE_USER,
KOBJ_NS_TYPES
};
--
2.26.0
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