// SPDX-License-Identifier: GPL-2.0 /* * fs/f2fs/verity.c: fs-verity support for f2fs * * Copyright 2019 Google LLC */ /* * Implementation of fsverity_operations for f2fs. * * Like ext4, f2fs stores the verity metadata (Merkle tree and * fsverity_descriptor) past the end of the file, starting at the first 64K * boundary beyond i_size. This approach works because (a) verity files are * readonly, and (b) pages fully beyond i_size aren't visible to userspace but * can be read/written internally by f2fs with only some relatively small * changes to f2fs. Extended attributes cannot be used because (a) f2fs limits * the total size of an inode's xattr entries to 4096 bytes, which wouldn't be * enough for even a single Merkle tree block, and (b) f2fs encryption doesn't * encrypt xattrs, yet the verity metadata *must* be encrypted when the file is * because it contains hashes of the plaintext data. * * Using a 64K boundary rather than a 4K one keeps things ready for * architectures with 64K pages, and it doesn't necessarily waste space on-disk * since there can be a hole between i_size and the start of the Merkle tree. */ #include #include "f2fs.h" #include "xattr.h" #define F2FS_VERIFY_VER (1) static inline loff_t f2fs_verity_metadata_pos(const struct inode *inode) { return round_up(inode->i_size, 65536); } /* * Read some verity metadata from the inode. __vfs_read() can't be used because * we need to read beyond i_size. */ static int pagecache_read(struct inode *inode, void *buf, size_t count, loff_t pos) { while (count) { size_t n = min_t(size_t, count, PAGE_SIZE - offset_in_page(pos)); struct page *page; void *addr; page = read_mapping_page(inode->i_mapping, pos >> PAGE_SHIFT, NULL); if (IS_ERR(page)) return PTR_ERR(page); addr = kmap_atomic(page); memcpy(buf, addr + offset_in_page(pos), n); kunmap_atomic(addr); put_page(page); buf += n; pos += n; count -= n; } return 0; } /* * Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY. * kernel_write() can't be used because the file descriptor is readonly. */ static int pagecache_write(struct inode *inode, const void *buf, size_t count, loff_t pos) { if (pos + count > inode->i_sb->s_maxbytes) return -EFBIG; while (count) { size_t n = min_t(size_t, count, PAGE_SIZE - offset_in_page(pos)); struct page *page; void *fsdata; void *addr; int res; res = pagecache_write_begin(NULL, inode->i_mapping, pos, n, 0, &page, &fsdata); if (res) return res; addr = kmap_atomic(page); memcpy(addr + offset_in_page(pos), buf, n); kunmap_atomic(addr); res = pagecache_write_end(NULL, inode->i_mapping, pos, n, n, page, fsdata); if (res < 0) return res; if (res != n) return -EIO; buf += n; pos += n; count -= n; } return 0; } /* * Format of f2fs verity xattr. This points to the location of the verity * descriptor within the file data rather than containing it directly because * the verity descriptor *must* be encrypted when f2fs encryption is used. But, * f2fs encryption does not encrypt xattrs. */ struct fsverity_descriptor_location { __le32 version; __le32 size; __le64 pos; }; static int f2fs_begin_enable_verity(struct file *filp) { struct inode *inode = file_inode(filp); int err; if (f2fs_verity_in_progress(inode)) return -EBUSY; if (f2fs_is_atomic_file(inode) || f2fs_is_volatile_file(inode)) return -EOPNOTSUPP; /* * Since the file was opened readonly, we have to initialize the quotas * here and not rely on ->open() doing it. This must be done before * evicting the inline data. */ err = f2fs_dquot_initialize(inode); if (err) return err; err = f2fs_convert_inline_inode(inode); if (err) return err; set_inode_flag(inode, FI_VERITY_IN_PROGRESS); return 0; } static int f2fs_end_enable_verity(struct file *filp, const void *desc, size_t desc_size, u64 merkle_tree_size) { struct inode *inode = file_inode(filp); struct f2fs_sb_info *sbi = F2FS_I_SB(inode); u64 desc_pos = f2fs_verity_metadata_pos(inode) + merkle_tree_size; struct fsverity_descriptor_location dloc = { .version = cpu_to_le32(F2FS_VERIFY_VER), .size = cpu_to_le32(desc_size), .pos = cpu_to_le64(desc_pos), }; int err = 0, err2 = 0; /* * If an error already occurred (which fs/verity/ signals by passing * desc == NULL), then only clean-up is needed. */ if (desc == NULL) goto cleanup; /* Append the verity descriptor. */ err = pagecache_write(inode, desc, desc_size, desc_pos); if (err) goto cleanup; /* * Write all pages (both data and verity metadata). Note that this must * happen before clearing FI_VERITY_IN_PROGRESS; otherwise pages beyond * i_size won't be written properly. For crash consistency, this also * must happen before the verity inode flag gets persisted. */ err = filemap_write_and_wait(inode->i_mapping); if (err) goto cleanup; /* Set the verity xattr. */ err = f2fs_setxattr(inode, F2FS_XATTR_INDEX_VERITY, F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc), NULL, XATTR_CREATE); if (err) goto cleanup; /* Finally, set the verity inode flag. */ file_set_verity(inode); f2fs_set_inode_flags(inode); f2fs_mark_inode_dirty_sync(inode, true); clear_inode_flag(inode, FI_VERITY_IN_PROGRESS); return 0; cleanup: /* * Verity failed to be enabled, so clean up by truncating any verity * metadata that was written beyond i_size (both from cache and from * disk) and clearing FI_VERITY_IN_PROGRESS. * * Taking i_gc_rwsem[WRITE] is needed to stop f2fs garbage collection * from re-instantiating cached pages we are truncating (since unlike * normal file accesses, garbage collection isn't limited by i_size). */ down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); truncate_inode_pages(inode->i_mapping, inode->i_size); err2 = f2fs_truncate(inode); if (err2) { f2fs_err(sbi, "Truncating verity metadata failed (errno=%d)", err2); set_sbi_flag(sbi, SBI_NEED_FSCK); } up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); clear_inode_flag(inode, FI_VERITY_IN_PROGRESS); return err ?: err2; } static int f2fs_get_verity_descriptor(struct inode *inode, void *buf, size_t buf_size) { struct fsverity_descriptor_location dloc; int res; u32 size; u64 pos; /* Get the descriptor location */ res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_VERITY, F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc), NULL); if (res < 0 && res != -ERANGE) return res; if (res != sizeof(dloc) || dloc.version != cpu_to_le32(F2FS_VERIFY_VER)) { f2fs_warn(F2FS_I_SB(inode), "unknown verity xattr format"); return -EINVAL; } size = le32_to_cpu(dloc.size); pos = le64_to_cpu(dloc.pos); /* Get the descriptor */ if (pos + size < pos || pos + size > inode->i_sb->s_maxbytes || pos < f2fs_verity_metadata_pos(inode) || size > INT_MAX) { f2fs_warn(F2FS_I_SB(inode), "invalid verity xattr"); return -EFSCORRUPTED; } if (buf_size) { if (size > buf_size) return -ERANGE; res = pagecache_read(inode, buf, size, pos); if (res) return res; } return size; } static struct page *f2fs_read_merkle_tree_page(struct inode *inode, pgoff_t index, unsigned long num_ra_pages) { DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index); struct page *page; index += f2fs_verity_metadata_pos(inode) >> PAGE_SHIFT; page = find_get_page_flags(inode->i_mapping, index, FGP_ACCESSED); if (!page || !PageUptodate(page)) { if (page) put_page(page); else if (num_ra_pages > 1) page_cache_ra_unbounded(&ractl, num_ra_pages, 0); page = read_mapping_page(inode->i_mapping, index, NULL); } return page; } static int f2fs_write_merkle_tree_block(struct inode *inode, const void *buf, u64 index, int log_blocksize) { loff_t pos = f2fs_verity_metadata_pos(inode) + (index << log_blocksize); return pagecache_write(inode, buf, 1 << log_blocksize, pos); } const struct fsverity_operations f2fs_verityops = { .begin_enable_verity = f2fs_begin_enable_verity, .end_enable_verity = f2fs_end_enable_verity, .get_verity_descriptor = f2fs_get_verity_descriptor, .read_merkle_tree_page = f2fs_read_merkle_tree_page, .write_merkle_tree_block = f2fs_write_merkle_tree_block, };