diff options
| -rw-r--r-- | fs/fs_context.c | 1 | ||||
| -rw-r--r-- | fs/fsopen.c | 12 | ||||
| -rw-r--r-- | fs/super.c | 36 | ||||
| -rw-r--r-- | include/linux/fs_context.h | 1 | ||||
| -rw-r--r-- | include/uapi/linux/mount.h | 3 |
5 files changed, 41 insertions, 12 deletions
diff --git a/fs/fs_context.c b/fs/fs_context.c index 851214d1d013..30d82d2979af 100644 --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -692,6 +692,7 @@ void vfs_clean_context(struct fs_context *fc) security_free_mnt_opts(&fc->security); kfree(fc->source); fc->source = NULL; + fc->exclusive = false; fc->purpose = FS_CONTEXT_FOR_RECONFIGURE; fc->phase = FS_CONTEXT_AWAITING_RECONF; diff --git a/fs/fsopen.c b/fs/fsopen.c index a69b7c9cc59c..ce03f6521c88 100644 --- a/fs/fsopen.c +++ b/fs/fsopen.c @@ -209,7 +209,7 @@ err: return ret; } -static int vfs_cmd_create(struct fs_context *fc) +static int vfs_cmd_create(struct fs_context *fc, bool exclusive) { struct super_block *sb; int ret; @@ -220,7 +220,12 @@ static int vfs_cmd_create(struct fs_context *fc) if (!mount_capable(fc)) return -EPERM; + /* require the new mount api */ + if (exclusive && fc->ops == &legacy_fs_context_ops) + return -EOPNOTSUPP; + fc->phase = FS_CONTEXT_CREATING; + fc->exclusive = exclusive; ret = vfs_get_tree(fc); if (ret) { @@ -284,7 +289,9 @@ static int vfs_fsconfig_locked(struct fs_context *fc, int cmd, return ret; switch (cmd) { case FSCONFIG_CMD_CREATE: - return vfs_cmd_create(fc); + return vfs_cmd_create(fc, false); + case FSCONFIG_CMD_CREATE_EXCL: + return vfs_cmd_create(fc, true); case FSCONFIG_CMD_RECONFIGURE: return vfs_cmd_reconfigure(fc); default: @@ -381,6 +388,7 @@ SYSCALL_DEFINE5(fsconfig, return -EINVAL; break; case FSCONFIG_CMD_CREATE: + case FSCONFIG_CMD_CREATE_EXCL: case FSCONFIG_CMD_RECONFIGURE: if (_key || _value || aux) return -EINVAL; diff --git a/fs/super.c b/fs/super.c index 96bec768684a..e04a403dbffd 100644 --- a/fs/super.c +++ b/fs/super.c @@ -546,17 +546,31 @@ bool mount_capable(struct fs_context *fc) * @test: Comparison callback * @set: Setup callback * - * Find or create a superblock using the parameters stored in the filesystem - * context and the two callback functions. + * Create a new superblock or find an existing one. * - * If an extant superblock is matched, then that will be returned with an - * elevated reference count that the caller must transfer or discard. + * The @test callback is used to find a matching existing superblock. + * Whether or not the requested parameters in @fc are taken into account + * is specific to the @test callback that is used. They may even be + * completely ignored. + * + * If an extant superblock is matched, it will be returned unless: + * + * (1) the namespace the filesystem context @fc and the extant + * superblock's namespace differ + * + * (2) the filesystem context @fc has requested that reusing an extant + * superblock is not allowed + * + * In both cases EBUSY will be returned. * * If no match is made, a new superblock will be allocated and basic - * initialisation will be performed (s_type, s_fs_info and s_id will be set and - * the set() callback will be invoked), the superblock will be published and it - * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE - * as yet unset. + * initialisation will be performed (s_type, s_fs_info and s_id will be + * set and the @set callback will be invoked), the superblock will be + * published and it will be returned in a partially constructed state + * with SB_BORN and SB_ACTIVE as yet unset. + * + * Return: On success, an extant or newly created superblock is + * returned. On failure an error pointer is returned. */ struct super_block *sget_fc(struct fs_context *fc, int (*test)(struct super_block *, struct fs_context *), @@ -603,9 +617,13 @@ retry: return s; share_extant_sb: - if (user_ns != old->s_user_ns) { + if (user_ns != old->s_user_ns || fc->exclusive) { spin_unlock(&sb_lock); destroy_unused_super(s); + if (fc->exclusive) + warnfc(fc, "reusing existing filesystem not allowed"); + else + warnfc(fc, "reusing existing filesystem in another namespace not allowed"); return ERR_PTR(-EBUSY); } if (!grab_super(old)) diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h index 851b3fe2549c..a33a3b1d9016 100644 --- a/include/linux/fs_context.h +++ b/include/linux/fs_context.h @@ -109,6 +109,7 @@ struct fs_context { bool need_free:1; /* Need to call ops->free() */ bool global:1; /* Goes into &init_user_ns */ bool oldapi:1; /* Coming from mount(2) */ + bool exclusive:1; /* create new superblock, reject existing one */ }; struct fs_context_operations { diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h index 8eb0d7b758d2..bb242fdcfe6b 100644 --- a/include/uapi/linux/mount.h +++ b/include/uapi/linux/mount.h @@ -100,8 +100,9 @@ enum fsconfig_command { FSCONFIG_SET_PATH = 3, /* Set parameter, supplying an object by path */ FSCONFIG_SET_PATH_EMPTY = 4, /* Set parameter, supplying an object by (empty) path */ FSCONFIG_SET_FD = 5, /* Set parameter, supplying an object by fd */ - FSCONFIG_CMD_CREATE = 6, /* Invoke superblock creation */ + FSCONFIG_CMD_CREATE = 6, /* Create new or reuse existing superblock */ FSCONFIG_CMD_RECONFIGURE = 7, /* Invoke superblock reconfiguration */ + FSCONFIG_CMD_CREATE_EXCL = 8, /* Create new superblock, fail if reusing existing superblock */ }; /* |