> -----Original Message----- > From: linux-btrfs-owner@xxxxxxxxxxxxxxx [mailto:linux-btrfs-owner@xxxxxxxxxxxxxxx] On Behalf Of Tomohiro Misono > Sent: Friday, May 11, 2018 3:26 PM > To: linux-btrfs@xxxxxxxxxxxxxxx > Subject: [PATCH v4 2/3] btrfs: Add unprivileged ioctl which returns subvolume's ROOT_REF > > Add unprivileged ioctl BTRFS_IOC_GET_SUBVOL_ROOTREF which returns ROOT_REF information of the subvolume containing this inode > except the subvolume name (this is because to prevent potential name leak). The subvolume name will be gained by user version of > ino_lookup ioctl (BTRFS_IOC_INO_LOOKUP_USER) which also performs permission check. > > The min id of root ref's subvolume to be searched is specified by @min_id in struct btrfs_ioctl_get_subvol_rootref_args. After the search > ends, @min_id is set to the last searched root ref's subvolid + 1. Also, if there are more root refs than > BTRFS_MAX_ROOTREF_BUFFER_NUM, -EOVERFLOW is returned. Therefore the caller can just call this ioctl again without changing the > argument to continue search. > > Signed-off-by: Tomohiro Misono <misono.tomohiro@xxxxxxxxxxxxxx> > --- > fs/btrfs/ioctl.c | 102 +++++++++++++++++++++++++++++++++++++++++++++ > include/uapi/linux/btrfs.h | 16 +++++++ > 2 files changed, 118 insertions(+) > > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 64b23e22852f..7988d328aed5 100644 > --- a/fs/btrfs/ioctl.c > +++ b/fs/btrfs/ioctl.c > @@ -2369,6 +2369,106 @@ static noinline int btrfs_ioctl_get_subvol_info(struct file *file, > return ret; > } > > +/* > + * Return ROOT_REF information of the subvolume contining this inode s/contining/containing > + * except the subvolume name. > + */ > +static noinline int btrfs_ioctl_get_subvol_rootref(struct file *file, > + void __user *argp) > +{ > + struct btrfs_ioctl_get_subvol_rootref_args *rootrefs; > + struct btrfs_root_ref *rref; > + struct btrfs_root *root; > + struct btrfs_path *path; > + struct btrfs_key key; > + > + struct extent_buffer *l; > + int slot; > + > + struct inode *inode; > + int i, nritems; > + int ret; > + u64 objectid; > + u8 found; > + > + path = btrfs_alloc_path(); > + if (!path) > + return -ENOMEM; > + > + rootrefs = memdup_user(argp, sizeof(*rootrefs)); > + if (!rootrefs) { > + btrfs_free_path(path); > + return -ENOMEM; > + } > + > + inode = file_inode(file); > + root = BTRFS_I(inode)->root->fs_info->tree_root; > + objectid = BTRFS_I(inode)->root->root_key.objectid; > + > + key.objectid = objectid; > + key.type = BTRFS_ROOT_REF_KEY; > + key.offset = rootrefs->min_id; > + found = 0; > + while (1) { > + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); > + if (ret < 0) { > + goto out; > + } else if (path->slots[0] >= > + btrfs_header_nritems(path->nodes[0])) { > + ret = btrfs_next_leaf(root, path); > + if (ret < 0) > + return ret; Should goto out; to do free work. > + } > + > + l = path->nodes[0]; > + slot = path->slots[0]; > + nritems = btrfs_header_nritems(l); > + if (nritems - slot == 0) { > + ret = 0; > + goto out; > + } > + > + for (i = slot; i < nritems; i++) { > + btrfs_item_key_to_cpu(l, &key, i); > + if (key.objectid != objectid || > + key.type != BTRFS_ROOT_REF_KEY) { > + ret = 0; > + goto out; > + } > + > + if (found == BTRFS_MAX_ROOTREF_BUFFER_NUM) { > + ret = -EOVERFLOW; > + goto out; > + } > + > + rref = btrfs_item_ptr(l, i, struct btrfs_root_ref); > + rootrefs->rootref[found].subvolid = key.offset; > + rootrefs->rootref[found].dirid = > + btrfs_root_ref_dirid(l, rref); > + found++; > + } > + > + btrfs_release_path(path); > + key.offset++; > + } Suggest to use btrfs_search_slot and btrfs_next_item to reduce counts of btrfs_search_slot. > + > +out: > + if (!ret || ret == -EOVERFLOW) { > + rootrefs->num_items = found; > + /* update min_id for next search */ > + if (found) > + rootrefs->min_id = > + rootrefs->rootref[found - 1].subvolid + 1; > + if (copy_to_user(argp, rootrefs, sizeof(*rootrefs))) > + ret = -EFAULT; > + } > + > + btrfs_free_path(path); > + kfree(rootrefs); > + > + return ret; > +} > + > static noinline int btrfs_ioctl_snap_destroy(struct file *file, > void __user *arg) > { > @@ -5503,6 +5603,8 @@ long btrfs_ioctl(struct file *file, unsigned int > return btrfs_ioctl_set_features(file, argp); > case BTRFS_IOC_GET_SUBVOL_INFO: > return btrfs_ioctl_get_subvol_info(file, argp); > + case BTRFS_IOC_GET_SUBVOL_ROOTREF: > + return btrfs_ioctl_get_subvol_rootref(file, argp); > } > > return -ENOTTY; > diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h index ed053852c71f..82c88d52d6e6 100644 > --- a/include/uapi/linux/btrfs.h > +++ b/include/uapi/linux/btrfs.h > @@ -774,6 +774,20 @@ struct btrfs_ioctl_get_subvol_info_args { > __u64 reserved[8]; > }; > > +#define BTRFS_MAX_ROOTREF_BUFFER_NUM 255 struct > +btrfs_ioctl_get_subvol_rootref_args { > + /* in/out, min id of rootref's subvolid to be searched */ > + __u64 min_id; > + /* out */ > + struct { > + __u64 subvolid; > + __u64 dirid; > + } rootref[BTRFS_MAX_ROOTREF_BUFFER_NUM]; > + /* out, number of found items */ > + __u8 num_items; > + __u8 align[7]; > +}; > + > /* Error codes as returned by the kernel */ enum btrfs_err_code { > BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1, @@ -894,5 +908,7 @@ enum btrfs_err_code { > struct btrfs_ioctl_logical_ino_args) #define BTRFS_IOC_GET_SUBVOL_INFO > _IOR(BTRFS_IOCTL_MAGIC, 60, \ > struct btrfs_ioctl_get_subvol_info_args) > +#define BTRFS_IOC_GET_SUBVOL_ROOTREF _IOWR(BTRFS_IOCTL_MAGIC, 61, \ > + struct btrfs_ioctl_get_subvol_rootref_args) > > #endif /* _UAPI_LINUX_BTRFS_H */ > -- > 2.14.3 > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > ?韬{.n?????%??檩??w?{.n???{饼?~镶?^n?■???h?璀?｛?夸z罐?+€?zf＂?????i?????_璁?:+v??撸?
