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Diffstat (limited to 'fs/super.c')
-rw-r--r--fs/super.c69
1 files changed, 61 insertions, 8 deletions
diff --git a/fs/super.c b/fs/super.c
index 5806ffd45563..c2ff475c1711 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -33,6 +33,7 @@
#include <linux/cleancache.h>
#include <linux/fsnotify.h>
#include <linux/lockdep.h>
+#include <linux/user_namespace.h>
#include "internal.h"
@@ -165,6 +166,7 @@ static void destroy_super(struct super_block *s)
list_lru_destroy(&s->s_inode_lru);
security_sb_free(s);
WARN_ON(!list_empty(&s->s_mounts));
+ put_user_ns(s->s_user_ns);
kfree(s->s_subtype);
kfree(s->s_options);
call_rcu(&s->rcu, destroy_super_rcu);
@@ -174,11 +176,13 @@ static void destroy_super(struct super_block *s)
* alloc_super - create new superblock
* @type: filesystem type superblock should belong to
* @flags: the mount flags
+ * @user_ns: User namespace for the super_block
*
* Allocates and initializes a new &struct super_block. alloc_super()
* returns a pointer new superblock or %NULL if allocation had failed.
*/
-static struct super_block *alloc_super(struct file_system_type *type, int flags)
+static struct super_block *alloc_super(struct file_system_type *type, int flags,
+ struct user_namespace *user_ns)
{
struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
static const struct super_operations default_op;
@@ -188,6 +192,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
return NULL;
INIT_LIST_HEAD(&s->s_mounts);
+ s->s_user_ns = get_user_ns(user_ns);
if (security_sb_alloc(s))
goto fail;
@@ -201,6 +206,8 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
init_waitqueue_head(&s->s_writers.wait_unfrozen);
s->s_bdi = &noop_backing_dev_info;
s->s_flags = flags;
+ if (s->s_user_ns != &init_user_ns)
+ s->s_iflags |= SB_I_NODEV;
INIT_HLIST_NODE(&s->s_instances);
INIT_HLIST_BL_HEAD(&s->s_anon);
mutex_init(&s->s_sync_lock);
@@ -445,29 +452,42 @@ void generic_shutdown_super(struct super_block *sb)
EXPORT_SYMBOL(generic_shutdown_super);
/**
- * sget - find or create a superblock
+ * sget_userns - find or create a superblock
* @type: filesystem type superblock should belong to
* @test: comparison callback
* @set: setup callback
* @flags: mount flags
+ * @user_ns: User namespace for the super_block
* @data: argument to each of them
*/
-struct super_block *sget(struct file_system_type *type,
+struct super_block *sget_userns(struct file_system_type *type,
int (*test)(struct super_block *,void *),
int (*set)(struct super_block *,void *),
- int flags,
+ int flags, struct user_namespace *user_ns,
void *data)
{
struct super_block *s = NULL;
struct super_block *old;
int err;
+ if (!(flags & MS_KERNMOUNT) &&
+ !(type->fs_flags & FS_USERNS_MOUNT) &&
+ !capable(CAP_SYS_ADMIN))
+ return ERR_PTR(-EPERM);
retry:
spin_lock(&sb_lock);
if (test) {
hlist_for_each_entry(old, &type->fs_supers, s_instances) {
if (!test(old, data))
continue;
+ if (user_ns != old->s_user_ns) {
+ spin_unlock(&sb_lock);
+ if (s) {
+ up_write(&s->s_umount);
+ destroy_super(s);
+ }
+ return ERR_PTR(-EBUSY);
+ }
if (!grab_super(old))
goto retry;
if (s) {
@@ -480,7 +500,7 @@ retry:
}
if (!s) {
spin_unlock(&sb_lock);
- s = alloc_super(type, flags);
+ s = alloc_super(type, flags, user_ns);
if (!s)
return ERR_PTR(-ENOMEM);
goto retry;
@@ -503,6 +523,31 @@ retry:
return s;
}
+EXPORT_SYMBOL(sget_userns);
+
+/**
+ * sget - find or create a superblock
+ * @type: filesystem type superblock should belong to
+ * @test: comparison callback
+ * @set: setup callback
+ * @flags: mount flags
+ * @data: argument to each of them
+ */
+struct super_block *sget(struct file_system_type *type,
+ int (*test)(struct super_block *,void *),
+ int (*set)(struct super_block *,void *),
+ int flags,
+ void *data)
+{
+ struct user_namespace *user_ns = current_user_ns();
+
+ /* Ensure the requestor has permissions over the target filesystem */
+ if (!(flags & MS_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN))
+ return ERR_PTR(-EPERM);
+
+ return sget_userns(type, test, set, flags, user_ns, data);
+}
+
EXPORT_SYMBOL(sget);
void drop_super(struct super_block *sb)
@@ -920,12 +965,20 @@ static int ns_set_super(struct super_block *sb, void *data)
return set_anon_super(sb, NULL);
}
-struct dentry *mount_ns(struct file_system_type *fs_type, int flags,
- void *data, int (*fill_super)(struct super_block *, void *, int))
+struct dentry *mount_ns(struct file_system_type *fs_type,
+ int flags, void *data, void *ns, struct user_namespace *user_ns,
+ int (*fill_super)(struct super_block *, void *, int))
{
struct super_block *sb;
- sb = sget(fs_type, ns_test_super, ns_set_super, flags, data);
+ /* Don't allow mounting unless the caller has CAP_SYS_ADMIN
+ * over the namespace.
+ */
+ if (!(flags & MS_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN))
+ return ERR_PTR(-EPERM);
+
+ sb = sget_userns(fs_type, ns_test_super, ns_set_super, flags,
+ user_ns, ns);
if (IS_ERR(sb))
return ERR_CAST(sb);