From: Amir Goldstein <amir73il@gmail.com> mainline inclusion from mainline-v6.9-rc1 commit 44350256ab943d424d70aa60a34f45060b3a36e8 category: feature bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBHLU4 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- FUSE server calls the FUSE_DEV_IOC_BACKING_OPEN ioctl with a backing file descriptor. If the call succeeds, a backing file identifier is returned. A later change will be using this backing file id in a reply to OPEN request with the flag FOPEN_PASSTHROUGH to setup passthrough of file operations on the open FUSE file to the backing file. The FUSE server should call FUSE_DEV_IOC_BACKING_CLOSE ioctl to close the backing file by its id. This can be done at any time, but if an open reply with FOPEN_PASSTHROUGH flag is still in progress, the open may fail if the backing file is closed before the fuse file was opened. Setting up backing files requires a server with CAP_SYS_ADMIN privileges. For the backing file to be successfully setup, the backing file must implement both read_iter and write_iter file operations. The limitation on the level of filesystem stacking allowed for the backing file is enforced before setting up the backing file. Signed-off-by: Alessio Balsini <balsini@android.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Conflicts: fs/fuse/fuse_i.h Signed-off-by: Yifan Qiao <qiaoyifan4@huawei.com> --- fs/fuse/fuse_i.h | 10 +++ include/uapi/linux/fuse.h | 9 +++ fs/fuse/dev.c | 41 ++++++++++++ fs/fuse/inode.c | 5 ++ fs/fuse/passthrough.c | 136 ++++++++++++++++++++++++++++++++++++++ 5 files changed, 201 insertions(+) diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 350eb5ed5578..4d9a14db696b 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -80,6 +80,7 @@ struct fuse_submount_lookup { /** Container for data related to mapping to backing file */ struct fuse_backing { struct file *file; + struct cred *cred; /** refcount */ refcount_t count; @@ -909,6 +910,11 @@ struct fuse_conn { /* New writepages go into this bucket */ struct fuse_sync_bucket __rcu *curr_bucket; +#ifdef CONFIG_FUSE_PASSTHROUGH + /** IDR for backing files ids */ + struct idr backing_files_map; +#endif + KABI_RESERVE(1) KABI_RESERVE(2) KABI_RESERVE(3) @@ -1425,5 +1431,9 @@ static inline struct fuse_backing *fuse_inode_backing_set(struct fuse_inode *fi, struct fuse_backing *fuse_backing_get(struct fuse_backing *fb); void fuse_backing_put(struct fuse_backing *fb); +void fuse_backing_files_init(struct fuse_conn *fc); +void fuse_backing_files_free(struct fuse_conn *fc); +int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map); +int fuse_backing_close(struct fuse_conn *fc, int backing_id); #endif /* _FS_FUSE_I_H */ diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index 7bb6219cfda0..1162a47b6a42 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -1057,9 +1057,18 @@ struct fuse_notify_retrieve_in { uint64_t dummy4; }; +struct fuse_backing_map { + int32_t fd; + uint32_t flags; + uint64_t padding; +}; + /* Device ioctls: */ #define FUSE_DEV_IOC_MAGIC 229 #define FUSE_DEV_IOC_CLONE _IOR(FUSE_DEV_IOC_MAGIC, 0, uint32_t) +#define FUSE_DEV_IOC_BACKING_OPEN _IOW(FUSE_DEV_IOC_MAGIC, 1, \ + struct fuse_backing_map) +#define FUSE_DEV_IOC_BACKING_CLOSE _IOW(FUSE_DEV_IOC_MAGIC, 2, uint32_t) struct fuse_lseek_in { uint64_t fh; diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 117221e4d986..3c842286cdbb 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -2285,6 +2285,41 @@ static long fuse_dev_ioctl_clone(struct file *file, __u32 __user *argp) return res; } +static long fuse_dev_ioctl_backing_open(struct file *file, + struct fuse_backing_map __user *argp) +{ + struct fuse_dev *fud = fuse_get_dev(file); + struct fuse_backing_map map; + + if (!fud) + return -EPERM; + + if (!IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + return -EOPNOTSUPP; + + if (copy_from_user(&map, argp, sizeof(map))) + return -EFAULT; + + return fuse_backing_open(fud->fc, &map); +} + +static long fuse_dev_ioctl_backing_close(struct file *file, __u32 __user *argp) +{ + struct fuse_dev *fud = fuse_get_dev(file); + int backing_id; + + if (!fud) + return -EPERM; + + if (!IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + return -EOPNOTSUPP; + + if (get_user(backing_id, argp)) + return -EFAULT; + + return fuse_backing_close(fud->fc, backing_id); +} + static long fuse_dev_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { @@ -2294,6 +2329,12 @@ static long fuse_dev_ioctl(struct file *file, unsigned int cmd, case FUSE_DEV_IOC_CLONE: return fuse_dev_ioctl_clone(file, argp); + case FUSE_DEV_IOC_BACKING_OPEN: + return fuse_dev_ioctl_backing_open(file, argp); + + case FUSE_DEV_IOC_BACKING_CLOSE: + return fuse_dev_ioctl_backing_close(file, argp); + default: return -ENOTTY; } diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 89e77b136879..d5f9526b76ec 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -952,6 +952,9 @@ void fuse_conn_init(struct fuse_conn *fc, struct fuse_mount *fm, fc->max_pages = FUSE_DEFAULT_MAX_PAGES_PER_REQ; fc->max_pages_limit = FUSE_MAX_MAX_PAGES; + if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + fuse_backing_files_init(fc); + INIT_LIST_HEAD(&fc->mounts); list_add(&fm->fc_entry, &fc->mounts); fm->fc = fc; @@ -982,6 +985,8 @@ void fuse_conn_put(struct fuse_conn *fc) WARN_ON(atomic_read(&bucket->count) != 1); kfree(bucket); } + if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + fuse_backing_files_free(fc); call_rcu(&fc->rcu, delayed_release); } } diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c index e8639c0a9ac6..7ec92a54c2e0 100644 --- a/fs/fuse/passthrough.c +++ b/fs/fuse/passthrough.c @@ -18,8 +18,11 @@ struct fuse_backing *fuse_backing_get(struct fuse_backing *fb) static void fuse_backing_free(struct fuse_backing *fb) { + pr_debug("%s: fb=0x%p\n", __func__, fb); + if (fb->file) fput(fb->file); + put_cred(fb->cred); kfree_rcu(fb, rcu); } @@ -28,3 +31,136 @@ void fuse_backing_put(struct fuse_backing *fb) if (fb && refcount_dec_and_test(&fb->count)) fuse_backing_free(fb); } + +void fuse_backing_files_init(struct fuse_conn *fc) +{ + idr_init(&fc->backing_files_map); +} + +static int fuse_backing_id_alloc(struct fuse_conn *fc, struct fuse_backing *fb) +{ + int id; + + idr_preload(GFP_KERNEL); + spin_lock(&fc->lock); + /* FIXME: xarray might be space inefficient */ + id = idr_alloc_cyclic(&fc->backing_files_map, fb, 1, 0, GFP_ATOMIC); + spin_unlock(&fc->lock); + idr_preload_end(); + + WARN_ON_ONCE(id == 0); + return id; +} + +static struct fuse_backing *fuse_backing_id_remove(struct fuse_conn *fc, + int id) +{ + struct fuse_backing *fb; + + spin_lock(&fc->lock); + fb = idr_remove(&fc->backing_files_map, id); + spin_unlock(&fc->lock); + + return fb; +} + +static int fuse_backing_id_free(int id, void *p, void *data) +{ + struct fuse_backing *fb = p; + + WARN_ON_ONCE(refcount_read(&fb->count) != 1); + fuse_backing_free(fb); + return 0; +} + +void fuse_backing_files_free(struct fuse_conn *fc) +{ + idr_for_each(&fc->backing_files_map, fuse_backing_id_free, NULL); + idr_destroy(&fc->backing_files_map); +} + +int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map) +{ + struct file *file; + struct super_block *backing_sb; + struct fuse_backing *fb = NULL; + int res; + + pr_debug("%s: fd=%d flags=0x%x\n", __func__, map->fd, map->flags); + + /* TODO: relax CAP_SYS_ADMIN once backing files are visible to lsof */ + res = -EPERM; + if (!fc->passthrough || !capable(CAP_SYS_ADMIN)) + goto out; + + res = -EINVAL; + if (map->flags) + goto out; + + file = fget(map->fd); + res = -EBADF; + if (!file) + goto out; + + res = -EOPNOTSUPP; + if (!file->f_op->read_iter || !file->f_op->write_iter) + goto out_fput; + + backing_sb = file_inode(file)->i_sb; + res = -ELOOP; + if (backing_sb->s_stack_depth >= fc->max_stack_depth) + goto out_fput; + + fb = kmalloc(sizeof(struct fuse_backing), GFP_KERNEL); + res = -ENOMEM; + if (!fb) + goto out_fput; + + fb->file = file; + fb->cred = prepare_creds(); + refcount_set(&fb->count, 1); + + res = fuse_backing_id_alloc(fc, fb); + if (res < 0) { + fuse_backing_free(fb); + fb = NULL; + } + +out: + pr_debug("%s: fb=0x%p, ret=%i\n", __func__, fb, res); + + return res; + +out_fput: + fput(file); + goto out; +} + +int fuse_backing_close(struct fuse_conn *fc, int backing_id) +{ + struct fuse_backing *fb = NULL; + int err; + + pr_debug("%s: backing_id=%d\n", __func__, backing_id); + + /* TODO: relax CAP_SYS_ADMIN once backing files are visible to lsof */ + err = -EPERM; + if (!fc->passthrough || !capable(CAP_SYS_ADMIN)) + goto out; + + err = -EINVAL; + if (backing_id <= 0) + goto out; + + err = -ENOENT; + fb = fuse_backing_id_remove(fc, backing_id); + if (!fb) + goto out; + + fuse_backing_put(fb); + err = 0; +out: + pr_debug("%s: fb=0x%p, err=%i\n", __func__, fb, err); + + return err; +} -- 2.39.2