1 #include <linux/syscalls.h> 2 #include <linux/slab.h> 3 #include <linux/fs.h> 4 #include <linux/file.h> 5 #include <linux/mount.h> 6 #include <linux/namei.h> 7 #include <linux/exportfs.h> 8 #include <asm/uaccess.h> 9 #include "internal.h" 10 11 static long do_sys_name_to_handle(struct path *path, 12 struct file_handle __user *ufh, 13 int __user *mnt_id) 14 { 15 long retval; 16 struct file_handle f_handle; 17 int handle_dwords, handle_bytes; 18 struct file_handle *handle = NULL; 19 20 /* 21 * We need t make sure wether the file system 22 * support decoding of the file handle 23 */ 24 if (!path->mnt->mnt_sb->s_export_op || 25 !path->mnt->mnt_sb->s_export_op->fh_to_dentry) 26 return -EOPNOTSUPP; 27 28 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) 29 return -EFAULT; 30 31 if (f_handle.handle_bytes > MAX_HANDLE_SZ) 32 return -EINVAL; 33 34 handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes, 35 GFP_KERNEL); 36 if (!handle) 37 return -ENOMEM; 38 39 /* convert handle size to multiple of sizeof(u32) */ 40 handle_dwords = f_handle.handle_bytes >> 2; 41 42 /* we ask for a non connected handle */ 43 retval = exportfs_encode_fh(path->dentry, 44 (struct fid *)handle->f_handle, 45 &handle_dwords, 0); 46 handle->handle_type = retval; 47 /* convert handle size to bytes */ 48 handle_bytes = handle_dwords * sizeof(u32); 49 handle->handle_bytes = handle_bytes; 50 if ((handle->handle_bytes > f_handle.handle_bytes) || 51 (retval == 255) || (retval == -ENOSPC)) { 52 /* As per old exportfs_encode_fh documentation 53 * we could return ENOSPC to indicate overflow 54 * But file system returned 255 always. So handle 55 * both the values 56 */ 57 /* 58 * set the handle size to zero so we copy only 59 * non variable part of the file_handle 60 */ 61 handle_bytes = 0; 62 retval = -EOVERFLOW; 63 } else 64 retval = 0; 65 /* copy the mount id */ 66 if (copy_to_user(mnt_id, &path->mnt->mnt_id, sizeof(*mnt_id)) || 67 copy_to_user(ufh, handle, 68 sizeof(struct file_handle) + handle_bytes)) 69 retval = -EFAULT; 70 kfree(handle); 71 return retval; 72 } 73 74 /** 75 * sys_name_to_handle_at: convert name to handle 76 * @dfd: directory relative to which name is interpreted if not absolute 77 * @name: name that should be converted to handle. 78 * @handle: resulting file handle 79 * @mnt_id: mount id of the file system containing the file 80 * @flag: flag value to indicate whether to follow symlink or not 81 * 82 * @handle->handle_size indicate the space available to store the 83 * variable part of the file handle in bytes. If there is not 84 * enough space, the field is updated to return the minimum 85 * value required. 86 */ 87 SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name, 88 struct file_handle __user *, handle, int __user *, mnt_id, 89 int, flag) 90 { 91 struct path path; 92 int lookup_flags; 93 int err; 94 95 if ((flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) 96 return -EINVAL; 97 98 lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0; 99 if (flag & AT_EMPTY_PATH) 100 lookup_flags |= LOOKUP_EMPTY; 101 err = user_path_at(dfd, name, lookup_flags, &path); 102 if (!err) { 103 err = do_sys_name_to_handle(&path, handle, mnt_id); 104 path_put(&path); 105 } 106 return err; 107 } 108