diff --git a/fs/fhandle.c b/fs/fhandle.c index 218511f38cbb1..8339a10410254 100644 --- a/fs/fhandle.c +++ b/fs/fhandle.c @@ -31,6 +31,14 @@ static long do_sys_name_to_handle(const struct path *path, if (!exportfs_can_encode_fh(path->dentry->d_sb->s_export_op, fh_flags)) return -EOPNOTSUPP; + /* + * A request to encode a connectable handle for a disconnected dentry + * is unexpected since AT_EMPTY_PATH is not allowed. + */ + if (fh_flags & EXPORT_FH_CONNECTABLE && + WARN_ON(path->dentry->d_flags & DCACHE_DISCONNECTED)) + return -EINVAL; + if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) return -EFAULT; @@ -45,7 +53,7 @@ static long do_sys_name_to_handle(const struct path *path, /* convert handle size to multiple of sizeof(u32) */ handle_dwords = f_handle.handle_bytes >> 2; - /* we ask for a non connectable maybe decodeable file handle */ + /* Encode a possibly decodeable/connectable file handle */ retval = exportfs_encode_fh(path->dentry, (struct fid *)handle->f_handle, &handle_dwords, fh_flags); @@ -67,8 +75,23 @@ static long do_sys_name_to_handle(const struct path *path, * non variable part of the file_handle */ handle_bytes = 0; - } else + } else { + /* + * When asked to encode a connectable file handle, encode this + * property in the file handle itself, so that we later know + * how to decode it. + * For sanity, also encode in the file handle if the encoded + * object is a directory and verify this during decode, because + * decoding directory file handles is quite different than + * decoding connectable non-directory file handles. + */ + if (fh_flags & EXPORT_FH_CONNECTABLE) { + handle->handle_type |= FILEID_IS_CONNECTABLE; + if (d_is_dir(path->dentry)) + fh_flags |= FILEID_IS_DIR; + } retval = 0; + } /* copy the mount id */ if (unique_mntid) { if (put_user(real_mount(path->mnt)->mnt_id_unique, @@ -109,15 +132,30 @@ SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name, { struct path path; int lookup_flags; - int fh_flags; + int fh_flags = 0; int err; if (flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH | AT_HANDLE_FID | - AT_HANDLE_MNT_ID_UNIQUE)) + AT_HANDLE_MNT_ID_UNIQUE | AT_HANDLE_CONNECTABLE)) + return -EINVAL; + + /* + * AT_HANDLE_FID means there is no intention to decode file handle + * AT_HANDLE_CONNECTABLE means there is an intention to decode a + * connected fd (with known path), so these flags are conflicting. + * AT_EMPTY_PATH could be used along with a dfd that refers to a + * disconnected non-directory, which cannot be used to encode a + * connectable file handle, because its parent is unknown. + */ + if (flag & AT_HANDLE_CONNECTABLE && + flag & (AT_HANDLE_FID | AT_EMPTY_PATH)) return -EINVAL; + else if (flag & AT_HANDLE_FID) + fh_flags |= EXPORT_FH_FID; + else if (flag & AT_HANDLE_CONNECTABLE) + fh_flags |= EXPORT_FH_CONNECTABLE; lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0; - fh_flags = (flag & AT_HANDLE_FID) ? EXPORT_FH_FID : 0; if (flag & AT_EMPTY_PATH) lookup_flags |= LOOKUP_EMPTY; err = user_path_at(dfd, name, lookup_flags, &path); diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h index 5e14d4500a75c..4ee42b2cf4ab2 100644 --- a/include/linux/exportfs.h +++ b/include/linux/exportfs.h @@ -169,6 +169,8 @@ struct fid { #define FILEID_USER_FLAGS(type) ((type) & FILEID_USER_FLAGS_MASK) /* Flags supported in encoded handle_type that is exported to user */ +#define FILEID_IS_CONNECTABLE 0x10000 +#define FILEID_IS_DIR 0x20000 #define FILEID_VALID_USER_FLAGS (0) /** diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h index 87e2dec79fea4..56ff2100e0216 100644 --- a/include/uapi/linux/fcntl.h +++ b/include/uapi/linux/fcntl.h @@ -153,6 +153,7 @@ object identity and may not be usable with open_by_handle_at(2). */ #define AT_HANDLE_MNT_ID_UNIQUE 0x001 /* Return the u64 unique mount ID. */ +#define AT_HANDLE_CONNECTABLE 0x002 /* Request a connectable file handle */ #if defined(__KERNEL__) #define AT_GETATTR_NOSEC 0x80000000