diff options
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 136 |
1 files changed, 16 insertions, 120 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index ab467ee58341..bc0f15257b49 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -75,22 +75,6 @@ static DECLARE_RWSEM(namespace_sem); static HLIST_HEAD(unmounted); /* protected by namespace_sem */ static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */ -struct mnt_idmap { - struct user_namespace *owner; - refcount_t count; -}; - -/* - * Carries the initial idmapping of 0:0:4294967295 which is an identity - * mapping. This means that {g,u}id 0 is mapped to {g,u}id 0, {g,u}id 1 is - * mapped to {g,u}id 1, [...], {g,u}id 1000 to {g,u}id 1000, [...]. - */ -struct mnt_idmap nop_mnt_idmap = { - .owner = &init_user_ns, - .count = REFCOUNT_INIT(1), -}; -EXPORT_SYMBOL_GPL(nop_mnt_idmap); - struct mount_kattr { unsigned int attr_set; unsigned int attr_clr; @@ -210,104 +194,6 @@ int mnt_get_count(struct mount *mnt) #endif } -/** - * mnt_idmap_owner - retrieve owner of the mount's idmapping - * @idmap: mount idmapping - * - * This helper will go away once the conversion to use struct mnt_idmap - * everywhere has finished at which point the helper will be unexported. - * - * Only code that needs to perform permission checks based on the owner of the - * idmapping will get access to it. All other code will solely rely on - * idmappings. This will get us type safety so it's impossible to conflate - * filesystems idmappings with mount idmappings. - * - * Return: The owner of the idmapping. - */ -struct user_namespace *mnt_idmap_owner(const struct mnt_idmap *idmap) -{ - return idmap->owner; -} -EXPORT_SYMBOL_GPL(mnt_idmap_owner); - -/** - * mnt_user_ns - retrieve owner of an idmapped mount - * @mnt: the relevant vfsmount - * - * This helper will go away once the conversion to use struct mnt_idmap - * everywhere has finished at which point the helper will be unexported. - * - * Only code that needs to perform permission checks based on the owner of the - * idmapping will get access to it. All other code will solely rely on - * idmappings. This will get us type safety so it's impossible to conflate - * filesystems idmappings with mount idmappings. - * - * Return: The owner of the idmapped. - */ -struct user_namespace *mnt_user_ns(const struct vfsmount *mnt) -{ - struct mnt_idmap *idmap = mnt_idmap(mnt); - - /* Return the actual owner of the filesystem instead of the nop. */ - if (idmap == &nop_mnt_idmap && - !initial_idmapping(mnt->mnt_sb->s_user_ns)) - return mnt->mnt_sb->s_user_ns; - return mnt_idmap_owner(idmap); -} -EXPORT_SYMBOL_GPL(mnt_user_ns); - -/** - * alloc_mnt_idmap - allocate a new idmapping for the mount - * @mnt_userns: owning userns of the idmapping - * - * Allocate a new struct mnt_idmap which carries the idmapping of the mount. - * - * Return: On success a new idmap, on error an error pointer is returned. - */ -static struct mnt_idmap *alloc_mnt_idmap(struct user_namespace *mnt_userns) -{ - struct mnt_idmap *idmap; - - idmap = kzalloc(sizeof(struct mnt_idmap), GFP_KERNEL_ACCOUNT); - if (!idmap) - return ERR_PTR(-ENOMEM); - - idmap->owner = get_user_ns(mnt_userns); - refcount_set(&idmap->count, 1); - return idmap; -} - -/** - * mnt_idmap_get - get a reference to an idmapping - * @idmap: the idmap to bump the reference on - * - * If @idmap is not the @nop_mnt_idmap bump the reference count. - * - * Return: @idmap with reference count bumped if @not_mnt_idmap isn't passed. - */ -static inline struct mnt_idmap *mnt_idmap_get(struct mnt_idmap *idmap) -{ - if (idmap != &nop_mnt_idmap) - refcount_inc(&idmap->count); - - return idmap; -} - -/** - * mnt_idmap_put - put a reference to an idmapping - * @idmap: the idmap to put the reference on - * - * If this is a non-initial idmapping, put the reference count when a mount is - * released and free it if we're the last user. - */ -static inline void mnt_idmap_put(struct mnt_idmap *idmap) -{ - if (idmap != &nop_mnt_idmap && refcount_dec_and_test(&idmap->count)) { - put_user_ns(idmap->owner); - kfree(idmap); - } -} - static struct mount *alloc_vfsmnt(const char *name) { struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); @@ -1397,6 +1283,17 @@ struct vfsmount *mntget(struct vfsmount *mnt) } EXPORT_SYMBOL(mntget); +/* + * Make a mount point inaccessible to new lookups. + * Because there may still be current users, the caller MUST WAIT + * for an RCU grace period before destroying the mount point. + */ +void mnt_make_shortterm(struct vfsmount *mnt) +{ + if (mnt) + real_mount(mnt)->mnt_ns = NULL; +} + /** * path_is_mountpoint() - Check if path is a mount in the current namespace. * @path: path to check @@ -4094,7 +3991,7 @@ static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) * Creating an idmapped mount with the filesystem wide idmapping * doesn't make sense so block that. We don't allow mushy semantics. */ - if (mnt_idmap_owner(kattr->mnt_idmap) == fs_userns) + if (!check_fsmapping(kattr->mnt_idmap, m->mnt_sb)) return -EINVAL; /* @@ -4340,7 +4237,7 @@ static int build_mount_idmapped(const struct mount_attr *attr, size_t usize, * result. */ mnt_userns = container_of(ns, struct user_namespace, ns); - if (initial_idmapping(mnt_userns)) { + if (mnt_userns == &init_user_ns) { err = -EPERM; goto out_fput; } @@ -4573,8 +4470,8 @@ EXPORT_SYMBOL_GPL(kern_mount); void kern_unmount(struct vfsmount *mnt) { /* release long term mount so mount point can be released */ - if (!IS_ERR_OR_NULL(mnt)) { - real_mount(mnt)->mnt_ns = NULL; + if (!IS_ERR(mnt)) { + mnt_make_shortterm(mnt); synchronize_rcu(); /* yecchhh... */ mntput(mnt); } @@ -4586,8 +4483,7 @@ void kern_unmount_array(struct vfsmount *mnt[], unsigned int num) unsigned int i; for (i = 0; i < num; i++) - if (mnt[i]) - real_mount(mnt[i])->mnt_ns = NULL; + mnt_make_shortterm(mnt[i]); synchronize_rcu_expedited(); for (i = 0; i < num; i++) mntput(mnt[i]); |