[v3,2/5] btrfs: initial fsverity support

Message ID	c9335d862ee4ddc1f7193bbb06ca7313d9ff1b30.1617900170.git.boris@bur.io (mailing list archive)
State	Superseded
Headers	show Return-Path: <linux-fscrypt-owner@kernel.org> From: Boris Burkov <boris@bur.io> To: linux-btrfs@vger.kernel.org, kernel-team@fb.com, linux-fscrypt@vger.kernel.org Subject: [PATCH v3 2/5] btrfs: initial fsverity support Date: Thu, 8 Apr 2021 11:33:53 -0700 Message-Id: <c9335d862ee4ddc1f7193bbb06ca7313d9ff1b30.1617900170.git.boris@bur.io> In-Reply-To: <cover.1617900170.git.boris@bur.io> References: <cover.1617900170.git.boris@bur.io> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk
Series	btrfs: support fsverity \| expand [v3,0/5] btrfs: support fsverity [v3,1/5] btrfs: add compat_flags to btrfs_inode_item [v3,2/5] btrfs: initial fsverity support [v3,3/5] btrfs: check verity for reads of inline extents and holes [v3,4/5] btrfs: fallback to buffered io for verity files [v3,5/5] btrfs: verity metadata orphan items

On Fri, Apr 09, 2021 at 11:05:05AM -0700, Boris Burkov wrote: > On Thu, Apr 08, 2021 at 03:50:08PM -0700, Eric Biggers wrote: > > On Thu, Apr 08, 2021 at 11:33:53AM -0700, Boris Burkov wrote: > > > diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c > > > index f7a4ad86adee..e5282a8f566a 100644 > > > --- a/fs/btrfs/super.c > > > +++ b/fs/btrfs/super.c > > > @@ -1339,6 +1339,7 @@ static int btrfs_fill_super(struct super_block *sb, > > > sb->s_op = &btrfs_super_ops; > > > sb->s_d_op = &btrfs_dentry_operations; > > > sb->s_export_op = &btrfs_export_ops; > > > + sb->s_vop = &btrfs_verityops; > > > sb->s_xattr = btrfs_xattr_handlers; > > > sb->s_time_gran = 1; > > > > As the kernel test robot has hinted at, this line needs to be conditional on > > CONFIG_FS_VERITY. > > > > > +/* > > > + * Helper function for computing cache index for Merkle tree pages > > > + * @inode: verity file whose Merkle items we want. > > > + * @merkle_index: index of the page in the Merkle tree (as in > > > + * read_merkle_tree_page). > > > + * @ret_index: returned index in the inode's mapping > > > + * > > > + * Returns: 0 on success, -EFBIG if the location in the file would be beyond > > > + * sb->s_maxbytes. > > > + */ > > > +static int get_verity_mapping_index(struct inode *inode, > > > + pgoff_t merkle_index, > > > + pgoff_t *ret_index) > > > +{ > > > + /* > > > + * the file is readonly, so i_size can't change here. We jump > > > + * some pages past the last page to cache our merkles. The goal > > > + * is just to jump past any hugepages that might be mapped in. > > > + */ > > > + pgoff_t merkle_offset = 2048; > > > + u64 index = (i_size_read(inode) >> PAGE_SHIFT) + merkle_offset + merkle_index; > > > > Would it make more sense to align the page index to 2048, rather than adding > > 2048? Or are huge pages not necessarily aligned in the page cache? > > > > > + > > > + if (index > inode->i_sb->s_maxbytes >> PAGE_SHIFT) > > > + return -EFBIG; > > > > There's an off-by-one error here; it's considering the beginning of the page > > rather than the end of the page. > > > > > +/* > > > + * Insert and write inode items with a given key type and offset. > > > + * @inode: The inode to insert for. > > > + * @key_type: The key type to insert. > > > + * @offset: The item offset to insert at. > > > + * @src: Source data to write. > > > + * @len: Length of source data to write. > > > + * > > > + * Write len bytes from src into items of up to 1k length. > > > + * The inserted items will have key <ino, key_type, offset + off> where > > > + * off is consecutively increasing from 0 up to the last item ending at > > > + * offset + len. > > > + * > > > + * Returns 0 on success and a negative error code on failure. > > > + */ > > > +static int write_key_bytes(struct btrfs_inode *inode, u8 key_type, u64 offset, > > > + const char *src, u64 len) > > > +{ > > > + struct btrfs_trans_handle *trans; > > > + struct btrfs_path *path; > > > + struct btrfs_root *root = inode->root; > > > + struct extent_buffer *leaf; > > > + struct btrfs_key key; > > > + u64 orig_len = len; > > > + u64 copied = 0; > > > + unsigned long copy_bytes; > > > + unsigned long src_offset = 0; > > > + void *data; > > > + int ret; > > > + > > > + path = btrfs_alloc_path(); > > > + if (!path) > > > + return -ENOMEM; > > > + > > > + while (len > 0) { > > > + trans = btrfs_start_transaction(root, 1); > > > + if (IS_ERR(trans)) { > > > + ret = PTR_ERR(trans); > > > + break; > > > + } > > > + > > > + key.objectid = btrfs_ino(inode); > > > + key.offset = offset; > > > + key.type = key_type; > > > + > > > + /* > > > + * insert 1K at a time mostly to be friendly for smaller > > > + * leaf size filesystems > > > + */ > > > + copy_bytes = min_t(u64, len, 1024); > > > + > > > + ret = btrfs_insert_empty_item(trans, root, path, &key, copy_bytes); > > > + if (ret) { > > > + btrfs_end_transaction(trans); > > > + break; > > > + } > > > + > > > + leaf = path->nodes[0]; > > > + > > > + data = btrfs_item_ptr(leaf, path->slots[0], void); > > > + write_extent_buffer(leaf, src + src_offset, > > > + (unsigned long)data, copy_bytes); > > > + offset += copy_bytes; > > > + src_offset += copy_bytes; > > > + len -= copy_bytes; > > > + copied += copy_bytes; > > > + > > > + btrfs_release_path(path); > > > + btrfs_end_transaction(trans); > > > + } > > > + > > > + btrfs_free_path(path); > > > + > > > + if (!ret && copied != orig_len) > > > + ret = -EIO; > > > > The condition '!ret && copied != orig_len' at the end appears to be unnecessary, > > since this function doesn't do short writes. > > > > > +/* > > > + * fsverity op that gets the struct fsverity_descriptor. > > > + * fsverity does a two pass setup for reading the descriptor, in the first pass > > > + * it calls with buf_size = 0 to query the size of the descriptor, > > > + * and then in the second pass it actually reads the descriptor off > > > + * disk. > > > + */ > > > +static int btrfs_get_verity_descriptor(struct inode *inode, void *buf, > > > + size_t buf_size) > > > +{ > > > + size_t true_size; > > > + ssize_t ret = 0; > > > + struct btrfs_verity_descriptor_item item; > > > + > > > + memset(&item, 0, sizeof(item)); > > > + ret = read_key_bytes(BTRFS_I(inode), BTRFS_VERITY_DESC_ITEM_KEY, > > > + 0, (char *)&item, sizeof(item), NULL); > > > + if (ret < 0) > > > + return ret; > > > + > > > + true_size = btrfs_stack_verity_descriptor_size(&item); > > > + if (true_size > INT_MAX) > > > > true_size is a __le64 on-disk, so it technically should be __u64 here; otherwise > > its high 32 bits might be ignored. > > > > > +struct btrfs_verity_descriptor_item { > > > + /* size of the verity descriptor in bytes */ > > > + __le64 size; > > > + __le64 reserved[2]; > > > + __u8 encryption; > > > +} __attribute__ ((__packed__)); > > > > The 'reserved' field still isn't validated to be 0 before going ahead and using > > the descriptor. Is that still intentional? If so, it might be clearer to call > > this field 'unused'. > > > > I should have asked about this last time, sorry I didn't get around to > it. I'm not familiar with the implied semantics of something called > reserved vs unused, so if you wouldn't mind explaining that a bit more, > I would appreciate it. "reserved" normally means a field is reserved for future use, so unrecognized values result in an error (like an "incompat" flag). "unused" usually means the field is simply not used (like a "compat" flag). > > Thinking out loud, and apologies in advance that this is a bit naive: > Whether or not I validate it in kernel K1 will affect two things: not > accidentally putting junk in s.t. it is hard for K2 to properly use the > field, and it ensures that K1 can never understand the file if K2 uses > the field and we roll back to K1. Is that correct? 100% committing to > the latter seems like a negative, since I'm not sure the future use > can't be compatible. The validation against junk is nice, but I > personally don't know how critical it is. Currently, it feels sufficient > to always zero the item before filling it out and writing it to disk. Which you want depends on what sort of thing you are hoping to use this field for in the future. Usually failing to validate flags/fields causes more problems than not validating them, though. - Eric

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile index cec88a66bd6c..3dcf9bcc2326 100644 --- a/fs/btrfs/Makefile +++ b/fs/btrfs/Makefile @@ -36,6 +36,7 @@ btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o btrfs-$(CONFIG_BTRFS_FS_REF_VERIFY) += ref-verify.o btrfs-$(CONFIG_BLK_DEV_ZONED) += zoned.o +btrfs-$(CONFIG_FS_VERITY) += verity.o btrfs-$(CONFIG_BTRFS_FS_RUN_SANITY_TESTS) += tests/free-space-tests.o \ tests/extent-buffer-tests.o tests/btrfs-tests.o \ diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h index e8dbc8e848ce..4536548b9e79 100644 --- a/fs/btrfs/btrfs_inode.h +++ b/fs/btrfs/btrfs_inode.h @@ -51,6 +51,7 @@ enum { * the file range, inode's io_tree). */ BTRFS_INODE_NO_DELALLOC_FLUSH, + BTRFS_INODE_VERITY_IN_PROGRESS, }; /* in memory btrfs inode */ diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index d633c563164b..78cc4f44b85e 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -279,9 +279,10 @@ struct btrfs_super_block { #define BTRFS_FEATURE_COMPAT_SAFE_SET 0ULL #define BTRFS_FEATURE_COMPAT_SAFE_CLEAR 0ULL -#define BTRFS_FEATURE_COMPAT_RO_SUPP \ - (BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE | \ - BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID) +#define BTRFS_FEATURE_COMPAT_RO_SUPP \ + (BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE | \ + BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID | \ + BTRFS_FEATURE_COMPAT_RO_VERITY) #define BTRFS_FEATURE_COMPAT_RO_SAFE_SET 0ULL #define BTRFS_FEATURE_COMPAT_RO_SAFE_CLEAR 0ULL @@ -1473,6 +1474,11 @@ do { \ BTRFS_INODE_COMPRESS | \ BTRFS_INODE_ROOT_ITEM_INIT) +/* + * Inode compat flags + */ +#define BTRFS_INODE_VERITY (1 << 0) + struct btrfs_map_token { struct extent_buffer *eb; char *kaddr; @@ -3721,6 +3727,17 @@ static inline int btrfs_defrag_cancelled(struct btrfs_fs_info *fs_info) return signal_pending(current); } +/* verity.c */ +extern const struct fsverity_operations btrfs_verityops; +int btrfs_drop_verity_items(struct btrfs_inode *inode); +BTRFS_SETGET_FUNCS(verity_descriptor_encryption, struct btrfs_verity_descriptor_item, + encryption, 8); +BTRFS_SETGET_FUNCS(verity_descriptor_size, struct btrfs_verity_descriptor_item, size, 64); +BTRFS_SETGET_STACK_FUNCS(stack_verity_descriptor_encryption, struct btrfs_verity_descriptor_item, + encryption, 8); +BTRFS_SETGET_STACK_FUNCS(stack_verity_descriptor_size, struct btrfs_verity_descriptor_item, + size, 64); + /* Sanity test specific functions */ #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS void btrfs_test_destroy_inode(struct inode *inode); diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 5b2a8a314adf..bf784c10040b 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -13,6 +13,7 @@ #include <linux/pagevec.h> #include <linux/prefetch.h> #include <linux/cleancache.h> +#include <linux/fsverity.h> #include "misc.h" #include "extent_io.h" #include "extent-io-tree.h" @@ -2862,15 +2863,28 @@ static void begin_page_read(struct btrfs_fs_info *fs_info, struct page *page) btrfs_subpage_start_reader(fs_info, page, page_offset(page), PAGE_SIZE); } -static void end_page_read(struct page *page, bool uptodate, u64 start, u32 len) +static int end_page_read(struct page *page, bool uptodate, u64 start, u32 len) { - struct btrfs_fs_info *fs_info = btrfs_sb(page->mapping->host->i_sb); + int ret = 0; + struct inode *inode = page->mapping->host; + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); ASSERT(page_offset(page) <= start && start + len <= page_offset(page) + PAGE_SIZE); if (uptodate) { - btrfs_page_set_uptodate(fs_info, page, start, len); + /* + * buffered reads of a file with page alignment will issue a + * 0 length read for one page past the end of file, so we must + * explicitly skip checking verity on that page of zeros. + */ + if (!PageError(page) && !PageUptodate(page) && + start < i_size_read(inode) && + fsverity_active(inode) && + !fsverity_verify_page(page)) + ret = -EIO; + else + btrfs_page_set_uptodate(fs_info, page, start, len); } else { btrfs_page_clear_uptodate(fs_info, page, start, len); btrfs_page_set_error(fs_info, page, start, len); @@ -2878,12 +2892,13 @@ static void end_page_read(struct page *page, bool uptodate, u64 start, u32 len) if (fs_info->sectorsize == PAGE_SIZE) unlock_page(page); - else if (is_data_inode(page->mapping->host)) + else if (is_data_inode(inode)) /* * For subpage data, unlock the page if we're the last reader. * For subpage metadata, page lock is not utilized for read. */ btrfs_subpage_end_reader(fs_info, page, start, len); + return ret; } /* @@ -3059,7 +3074,9 @@ static void end_bio_extent_readpage(struct bio *bio) bio_offset += len; /* Update page status and unlock */ - end_page_read(page, uptodate, start, len); + ret = end_page_read(page, uptodate, start, len); + if (ret) + uptodate = 0; endio_readpage_release_extent(&processed, BTRFS_I(inode), start, end, uptodate); } diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 42634658815f..e8dcada0d239 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -16,6 +16,7 @@ #include <linux/btrfs.h> #include <linux/uio.h> #include <linux/iversion.h> +#include <linux/fsverity.h> #include "ctree.h" #include "disk-io.h" #include "transaction.h" @@ -3578,7 +3579,12 @@ static loff_t btrfs_file_llseek(struct file *file, loff_t offset, int whence) static int btrfs_file_open(struct inode *inode, struct file *filp) { + int ret; filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC; + + ret = fsverity_file_open(inode, filp); + if (ret) + return ret; return generic_file_open(inode, filp); } diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 3aa96ec27045..887e1ca2ed66 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -32,6 +32,7 @@ #include <linux/sched/mm.h> #include <linux/iomap.h> #include <asm/unaligned.h> +#include <linux/fsverity.h> #include "misc.h" #include "ctree.h" #include "disk-io.h" @@ -5401,7 +5402,9 @@ void btrfs_evict_inode(struct inode *inode) trace_btrfs_inode_evict(inode); + if (!root) { + fsverity_cleanup_inode(inode); clear_inode(inode); return; } @@ -5484,6 +5487,7 @@ void btrfs_evict_inode(struct inode *inode) * to retry these periodically in the future. */ btrfs_remove_delayed_node(BTRFS_I(inode)); + fsverity_cleanup_inode(inode); clear_inode(inode); } @@ -9043,6 +9047,7 @@ static int btrfs_getattr(struct user_namespace *mnt_userns, struct inode *inode = d_inode(path->dentry); u32 blocksize = inode->i_sb->s_blocksize; u32 bi_flags = BTRFS_I(inode)->flags; + u32 bi_compat_flags = BTRFS_I(inode)->compat_flags; stat->result_mask |= STATX_BTIME; stat->btime.tv_sec = BTRFS_I(inode)->i_otime.tv_sec; @@ -9055,6 +9060,8 @@ static int btrfs_getattr(struct user_namespace *mnt_userns, stat->attributes |= STATX_ATTR_IMMUTABLE; if (bi_flags & BTRFS_INODE_NODUMP) stat->attributes |= STATX_ATTR_NODUMP; + if (bi_compat_flags & BTRFS_INODE_VERITY) + stat->attributes |= STATX_ATTR_VERITY; stat->attributes_mask |= (STATX_ATTR_APPEND | STATX_ATTR_COMPRESSED | diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 2c9cbd2642b1..4ec5735cff9b 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -26,6 +26,7 @@ #include <linux/btrfs.h> #include <linux/uaccess.h> #include <linux/iversion.h> +#include <linux/fsverity.h> #include "ctree.h" #include "disk-io.h" #include "export.h" @@ -105,6 +106,7 @@ static unsigned int btrfs_mask_fsflags_for_type(struct inode *inode, static unsigned int btrfs_inode_flags_to_fsflags(struct btrfs_inode *binode) { unsigned int flags = binode->flags; + unsigned int compat_flags = binode->compat_flags; unsigned int iflags = 0; if (flags & BTRFS_INODE_SYNC) @@ -121,6 +123,8 @@ static unsigned int btrfs_inode_flags_to_fsflags(struct btrfs_inode *binode) iflags |= FS_DIRSYNC_FL; if (flags & BTRFS_INODE_NODATACOW) iflags |= FS_NOCOW_FL; + if (compat_flags & BTRFS_INODE_VERITY) + iflags |= FS_VERITY_FL; if (flags & BTRFS_INODE_NOCOMPRESS) iflags |= FS_NOCOMP_FL; @@ -148,10 +152,12 @@ void btrfs_sync_inode_flags_to_i_flags(struct inode *inode) new_fl |= S_NOATIME; if (binode->flags & BTRFS_INODE_DIRSYNC) new_fl |= S_DIRSYNC; + if (binode->compat_flags & BTRFS_INODE_VERITY) + new_fl |= S_VERITY; set_mask_bits(&inode->i_flags, - S_SYNC | S_APPEND | S_IMMUTABLE | S_NOATIME | S_DIRSYNC, - new_fl); + S_SYNC | S_APPEND | S_IMMUTABLE | S_NOATIME | S_DIRSYNC | + S_VERITY, new_fl); } static int btrfs_ioctl_getflags(struct file *file, void __user *arg) @@ -5055,6 +5061,10 @@ long btrfs_ioctl(struct file *file, unsigned int return btrfs_ioctl_get_subvol_rootref(file, argp); case BTRFS_IOC_INO_LOOKUP_USER: return btrfs_ioctl_ino_lookup_user(file, argp); + case FS_IOC_ENABLE_VERITY: + return fsverity_ioctl_enable(file, (const void __user *)argp); + case FS_IOC_MEASURE_VERITY: + return fsverity_ioctl_measure(file, argp); } return -ENOTTY; diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index f7a4ad86adee..e5282a8f566a 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1339,6 +1339,7 @@ static int btrfs_fill_super(struct super_block *sb, sb->s_op = &btrfs_super_ops; sb->s_d_op = &btrfs_dentry_operations; sb->s_export_op = &btrfs_export_ops; + sb->s_vop = &btrfs_verityops; sb->s_xattr = btrfs_xattr_handlers; sb->s_time_gran = 1; #ifdef CONFIG_BTRFS_FS_POSIX_ACL diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index 6eb1c50fa98c..e8de0055c61e 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -267,6 +267,9 @@ BTRFS_FEAT_ATTR_INCOMPAT(raid1c34, RAID1C34); #ifdef CONFIG_BTRFS_DEBUG BTRFS_FEAT_ATTR_INCOMPAT(zoned, ZONED); #endif +#ifdef CONFIG_FS_VERITY +BTRFS_FEAT_ATTR_COMPAT_RO(verity, VERITY); +#endif static struct attribute *btrfs_supported_feature_attrs[] = { BTRFS_FEAT_ATTR_PTR(mixed_backref), @@ -284,6 +287,9 @@ static struct attribute *btrfs_supported_feature_attrs[] = { BTRFS_FEAT_ATTR_PTR(raid1c34), #ifdef CONFIG_BTRFS_DEBUG BTRFS_FEAT_ATTR_PTR(zoned), +#endif +#ifdef CONFIG_FS_VERITY + BTRFS_FEAT_ATTR_PTR(verity), #endif NULL }; diff --git a/fs/btrfs/verity.c b/fs/btrfs/verity.c new file mode 100644 index 000000000000..0cc9bdd876e2 --- /dev/null +++ b/fs/btrfs/verity.c @@ -0,0 +1,614 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2020 Facebook. All rights reserved. + */ + +#include <linux/init.h> +#include <linux/fs.h> +#include <linux/slab.h> +#include <linux/rwsem.h> +#include <linux/xattr.h> +#include <linux/security.h> +#include <linux/posix_acl_xattr.h> +#include <linux/iversion.h> +#include <linux/fsverity.h> +#include <linux/sched/mm.h> +#include "ctree.h" +#include "btrfs_inode.h" +#include "transaction.h" +#include "disk-io.h" +#include "locking.h" + +/* + * Just like ext4, we cache the merkle tree in pages after EOF in the page + * cache. Unlike ext4, we're storing these in dedicated btree items and + * not just shoving them after EOF in the file. This means we'll need to + * do extra work to encrypt them once encryption is supported in btrfs, + * but btrfs has a lot of careful code around i_size and it seems better + * to make a new key type than try and adjust all of our expectations + * for i_size. + * + * fs verity items are stored under two different key types on disk. + * + * The descriptor items: + * [ inode objectid, BTRFS_VERITY_DESC_ITEM_KEY, offset ] + * + * At offset 0, we store a btrfs_verity_descriptor_item which tracks the + * size of the descriptor item and some extra data for encryption. + * Starting at offset 1, these hold the generic fs verity descriptor. + * These are opaque to btrfs, we just read and write them as a blob for + * the higher level verity code. The most common size for this is 256 bytes. + * + * The merkle tree items: + * [ inode objectid, BTRFS_VERITY_MERKLE_ITEM_KEY, offset ] + * + * These also start at offset 0, and correspond to the merkle tree bytes. + * So when fsverity asks for page 0 of the merkle tree, we pull up one page + * starting at offset 0 for this key type. These are also opaque to btrfs, + * we're blindly storing whatever fsverity sends down. + * + * This file is just reading and writing the various items whenever + * fsverity needs us to. + */ + +/* + * Helper function for computing cache index for Merkle tree pages + * @inode: verity file whose Merkle items we want. + * @merkle_index: index of the page in the Merkle tree (as in + * read_merkle_tree_page). + * @ret_index: returned index in the inode's mapping + * + * Returns: 0 on success, -EFBIG if the location in the file would be beyond + * sb->s_maxbytes. + */ +static int get_verity_mapping_index(struct inode *inode, + pgoff_t merkle_index, + pgoff_t *ret_index) +{ + /* + * the file is readonly, so i_size can't change here. We jump + * some pages past the last page to cache our merkles. The goal + * is just to jump past any hugepages that might be mapped in. + */ + pgoff_t merkle_offset = 2048; + u64 index = (i_size_read(inode) >> PAGE_SHIFT) + merkle_offset + merkle_index; + + if (index > inode->i_sb->s_maxbytes >> PAGE_SHIFT) + return -EFBIG; + + *ret_index = index; + return 0; +} + + +/* + * Drop all the items for this inode with this key_type. + * @inode: The inode to drop items for + * @key_type: The type of items to drop (VERITY_DESC_ITEM or + * VERITY_MERKLE_ITEM) + * + * Before doing a verity enable we cleanup any existing verity items. + * + * This is also used to clean up if a verity enable failed half way + * through. + * + * Returns 0 on success, negative error code on failure. + */ +static int drop_verity_items(struct btrfs_inode *inode, u8 key_type) +{ + struct btrfs_trans_handle *trans; + struct btrfs_root *root = inode->root; + struct btrfs_path *path; + struct btrfs_key key; + int ret; + + path = btrfs_alloc_path(); + if (!path) + return -ENOMEM; + + while (1) { + trans = btrfs_start_transaction(root, 1); + if (IS_ERR(trans)) { + ret = PTR_ERR(trans); + goto out; + } + + /* + * walk backwards through all the items until we find one + * that isn't from our key type or objectid + */ + key.objectid = btrfs_ino(inode); + key.offset = (u64)-1; + key.type = key_type; + + ret = btrfs_search_slot(trans, root, &key, path, -1, 1); + if (ret > 0) { + ret = 0; + /* no more keys of this type, we're done */ + if (path->slots[0] == 0) + break; + path->slots[0]--; + } else if (ret < 0) { + break; + } + + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]); + + /* no more keys of this type, we're done */ + if (key.objectid != btrfs_ino(inode) || key.type != key_type) + break; + + /* + * this shouldn't be a performance sensitive function because + * it's not used as part of truncate. If it ever becomes + * perf sensitive, change this to walk forward and bulk delete + * items + */ + ret = btrfs_del_items(trans, root, path, + path->slots[0], 1); + btrfs_release_path(path); + btrfs_end_transaction(trans); + + if (ret) + goto out; + } + + btrfs_end_transaction(trans); +out: + btrfs_free_path(path); + return ret; + +} + +/* + * Insert and write inode items with a given key type and offset. + * @inode: The inode to insert for. + * @key_type: The key type to insert. + * @offset: The item offset to insert at. + * @src: Source data to write. + * @len: Length of source data to write. + * + * Write len bytes from src into items of up to 1k length. + * The inserted items will have key <ino, key_type, offset + off> where + * off is consecutively increasing from 0 up to the last item ending at + * offset + len. + * + * Returns 0 on success and a negative error code on failure. + */ +static int write_key_bytes(struct btrfs_inode *inode, u8 key_type, u64 offset, + const char *src, u64 len) +{ + struct btrfs_trans_handle *trans; + struct btrfs_path *path; + struct btrfs_root *root = inode->root; + struct extent_buffer *leaf; + struct btrfs_key key; + u64 orig_len = len; + u64 copied = 0; + unsigned long copy_bytes; + unsigned long src_offset = 0; + void *data; + int ret; + + path = btrfs_alloc_path(); + if (!path) + return -ENOMEM; + + while (len > 0) { + trans = btrfs_start_transaction(root, 1); + if (IS_ERR(trans)) { + ret = PTR_ERR(trans); + break; + } + + key.objectid = btrfs_ino(inode); + key.offset = offset; + key.type = key_type; + + /* + * insert 1K at a time mostly to be friendly for smaller + * leaf size filesystems + */ + copy_bytes = min_t(u64, len, 1024); + + ret = btrfs_insert_empty_item(trans, root, path, &key, copy_bytes); + if (ret) { + btrfs_end_transaction(trans); + break; + } + + leaf = path->nodes[0]; + + data = btrfs_item_ptr(leaf, path->slots[0], void); + write_extent_buffer(leaf, src + src_offset, + (unsigned long)data, copy_bytes); + offset += copy_bytes; + src_offset += copy_bytes; + len -= copy_bytes; + copied += copy_bytes; + + btrfs_release_path(path); + btrfs_end_transaction(trans); + } + + btrfs_free_path(path); + + if (!ret && copied != orig_len) + ret = -EIO; + return ret; +} + +/* + * Read inode items of the given key type and offset from the btree. + * @inode: The inode to read items of. + * @key_type: The key type to read. + * @offset: The item offset to read from. + * @dest: The buffer to read into. This parameter has slightly tricky + * semantics. If it is NULL, the function will not do any copying + * and will just return the size of all the items up to len bytes. + * If dest_page is passed, then the function will kmap_atomic the + * page and ignore dest, but it must still be non-NULL to avoid the + * counting-only behavior. + * @len: Length in bytes to read. + * @dest_page: Copy into this page instead of the dest buffer. + * + * Helper function to read items from the btree. This returns the number + * of bytes read or < 0 for errors. We can return short reads if the + * items don't exist on disk or aren't big enough to fill the desired length. + * + * Supports reading into a provided buffer (dest) or into the page cache + * + * Returns number of bytes read or a negative error code on failure. + */ +static ssize_t read_key_bytes(struct btrfs_inode *inode, u8 key_type, u64 offset, + char *dest, u64 len, struct page *dest_page) +{ + struct btrfs_path *path; + struct btrfs_root *root = inode->root; + struct extent_buffer *leaf; + struct btrfs_key key; + u64 item_end; + u64 copy_end; + u64 copied = 0; + u32 copy_offset; + unsigned long copy_bytes; + unsigned long dest_offset = 0; + void *data; + char *kaddr = dest; + int ret; + + path = btrfs_alloc_path(); + if (!path) + return -ENOMEM; + + if (dest_page) + path->reada = READA_FORWARD; + + key.objectid = btrfs_ino(inode); + key.offset = offset; + key.type = key_type; + + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); + if (ret < 0) { + goto out; + } else if (ret > 0) { + ret = 0; + if (path->slots[0] == 0) + goto out; + path->slots[0]--; + } + + while (len > 0) { + leaf = path->nodes[0]; + btrfs_item_key_to_cpu(leaf, &key, path->slots[0]); + + if (key.objectid != btrfs_ino(inode) || + key.type != key_type) + break; + + item_end = btrfs_item_size_nr(leaf, path->slots[0]) + key.offset; + + if (copied > 0) { + /* + * once we've copied something, we want all of the items + * to be sequential + */ + if (key.offset != offset) + break; + } else { + /* + * our initial offset might be in the middle of an + * item. Make sure it all makes sense + */ + if (key.offset > offset) + break; + if (item_end <= offset) + break; + } + + /* desc = NULL to just sum all the item lengths */ + if (!dest) + copy_end = item_end; + else + copy_end = min(offset + len, item_end); + + /* number of bytes in this item we want to copy */ + copy_bytes = copy_end - offset; + + /* offset from the start of item for copying */ + copy_offset = offset - key.offset; + + if (dest) { + if (dest_page) + kaddr = kmap_atomic(dest_page); + + data = btrfs_item_ptr(leaf, path->slots[0], void); + read_extent_buffer(leaf, kaddr + dest_offset, + (unsigned long)data + copy_offset, + copy_bytes); + + if (dest_page) + kunmap_atomic(kaddr); + } + + offset += copy_bytes; + dest_offset += copy_bytes; + len -= copy_bytes; + copied += copy_bytes; + + path->slots[0]++; + if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) { + /* + * we've reached the last slot in this leaf and we need + * to go to the next leaf. + */ + ret = btrfs_next_leaf(root, path); + if (ret < 0) { + break; + } else if (ret > 0) { + ret = 0; + break; + } + } + } +out: + btrfs_free_path(path); + if (!ret) + ret = copied; + return ret; +} + +/* + * fsverity op that begins enabling verity. + * fsverity calls this to ask us to setup the inode for enabling. We + * drop any existing verity items and set the in progress bit. + */ +static int btrfs_begin_enable_verity(struct file *filp) +{ + struct inode *inode = file_inode(filp); + int ret; + + if (test_bit(BTRFS_INODE_VERITY_IN_PROGRESS, &BTRFS_I(inode)->runtime_flags)) + return -EBUSY; + + /* + * ext4 adds the inode to the orphan list here, presumably because the + * truncate done at orphan processing time will delete partial + * measurements. TODO: setup orphans + */ + set_bit(BTRFS_INODE_VERITY_IN_PROGRESS, &BTRFS_I(inode)->runtime_flags); + ret = drop_verity_items(BTRFS_I(inode), BTRFS_VERITY_DESC_ITEM_KEY); + if (ret) + goto err; + + ret = drop_verity_items(BTRFS_I(inode), BTRFS_VERITY_MERKLE_ITEM_KEY); + if (ret) + goto err; + + return 0; + +err: + clear_bit(BTRFS_INODE_VERITY_IN_PROGRESS, &BTRFS_I(inode)->runtime_flags); + return ret; + +} + +/* + * fsverity op that ends enabling verity. + * fsverity calls this when it's done with all of the pages in the file + * and all of the merkle items have been inserted. We write the + * descriptor and update the inode in the btree to reflect its new life + * as a verity file. + */ +static int btrfs_end_enable_verity(struct file *filp, const void *desc, + size_t desc_size, u64 merkle_tree_size) +{ + struct btrfs_trans_handle *trans; + struct inode *inode = file_inode(filp); + struct btrfs_root *root = BTRFS_I(inode)->root; + struct btrfs_verity_descriptor_item item; + int ret; + + if (desc != NULL) { + /* write out the descriptor item */ + memset(&item, 0, sizeof(item)); + btrfs_set_stack_verity_descriptor_size(&item, desc_size); + ret = write_key_bytes(BTRFS_I(inode), + BTRFS_VERITY_DESC_ITEM_KEY, 0, + (const char *)&item, sizeof(item)); + if (ret) + goto out; + /* write out the descriptor itself */ + ret = write_key_bytes(BTRFS_I(inode), + BTRFS_VERITY_DESC_ITEM_KEY, 1, + desc, desc_size); + if (ret) + goto out; + + /* update our inode flags to include fs verity */ + trans = btrfs_start_transaction(root, 1); + if (IS_ERR(trans)) { + ret = PTR_ERR(trans); + goto out; + } + BTRFS_I(inode)->compat_flags |= BTRFS_INODE_VERITY; + btrfs_sync_inode_flags_to_i_flags(inode); + ret = btrfs_update_inode(trans, root, BTRFS_I(inode)); + btrfs_end_transaction(trans); + } + +out: + if (desc == NULL || ret) { + /* If we failed, drop all the verity items */ + drop_verity_items(BTRFS_I(inode), BTRFS_VERITY_DESC_ITEM_KEY); + drop_verity_items(BTRFS_I(inode), BTRFS_VERITY_MERKLE_ITEM_KEY); + } else + btrfs_set_fs_compat_ro(root->fs_info, VERITY); + clear_bit(BTRFS_INODE_VERITY_IN_PROGRESS, &BTRFS_I(inode)->runtime_flags); + return ret; +} + +/* + * fsverity op that gets the struct fsverity_descriptor. + * fsverity does a two pass setup for reading the descriptor, in the first pass + * it calls with buf_size = 0 to query the size of the descriptor, + * and then in the second pass it actually reads the descriptor off + * disk. + */ +static int btrfs_get_verity_descriptor(struct inode *inode, void *buf, + size_t buf_size) +{ + size_t true_size; + ssize_t ret = 0; + struct btrfs_verity_descriptor_item item; + + memset(&item, 0, sizeof(item)); + ret = read_key_bytes(BTRFS_I(inode), BTRFS_VERITY_DESC_ITEM_KEY, + 0, (char *)&item, sizeof(item), NULL); + if (ret < 0) + return ret; + + true_size = btrfs_stack_verity_descriptor_size(&item); + if (true_size > INT_MAX) + return -EUCLEAN; + if (!buf_size) + return true_size; + if (buf_size < true_size) + return -ERANGE; + + ret = read_key_bytes(BTRFS_I(inode), + BTRFS_VERITY_DESC_ITEM_KEY, 1, + buf, buf_size, NULL); + if (ret < 0) + return ret; + if (ret != true_size) + return -EIO; + + return true_size; +} + +/* + * fsverity op that reads and caches a merkle tree page. These are stored + * in the btree, but we cache them in the inode's address space after EOF. + */ +static struct page *btrfs_read_merkle_tree_page(struct inode *inode, + pgoff_t index, + unsigned long num_ra_pages) +{ + struct page *p; + u64 start = index << PAGE_SHIFT; + pgoff_t mapping_index; + ssize_t ret; + int err; + + err = get_verity_mapping_index(inode, index, &mapping_index); + if (err < 0) + return ERR_PTR(err); +again: + p = find_get_page_flags(inode->i_mapping, mapping_index, FGP_ACCESSED); + if (p) { + if (PageUptodate(p)) + return p; + + lock_page(p); + /* + * we only insert uptodate pages, so !Uptodate has to be + * an error + */ + if (!PageUptodate(p)) { + unlock_page(p); + put_page(p); + return ERR_PTR(-EIO); + } + unlock_page(p); + return p; + } + + p = page_cache_alloc(inode->i_mapping); + if (!p) + return ERR_PTR(-ENOMEM); + + /* + * merkle item keys are indexed from byte 0 in the merkle tree. + * they have the form: + * + * [ inode objectid, BTRFS_MERKLE_ITEM_KEY, offset in bytes ] + */ + ret = read_key_bytes(BTRFS_I(inode), + BTRFS_VERITY_MERKLE_ITEM_KEY, start, + page_address(p), PAGE_SIZE, p); + if (ret < 0) { + put_page(p); + return ERR_PTR(ret); + } + + /* zero fill any bytes we didn't write into the page */ + if (ret < PAGE_SIZE) { + char *kaddr = kmap_atomic(p); + + memset(kaddr + ret, 0, PAGE_SIZE - ret); + kunmap_atomic(kaddr); + } + SetPageUptodate(p); + err = add_to_page_cache_lru(p, inode->i_mapping, mapping_index, + mapping_gfp_mask(inode->i_mapping)); + + if (!err) { + /* inserted and ready for fsverity */ + unlock_page(p); + } else { + put_page(p); + /* did someone race us into inserting this page? */ + if (err == -EEXIST) + goto again; + p = ERR_PTR(err); + } + return p; +} + +/* + * fsverity op that writes a merkle tree block into the btree in 1k chunks. + */ +static int btrfs_write_merkle_tree_block(struct inode *inode, const void *buf, + u64 index, int log_blocksize) +{ + u64 start = index << log_blocksize; + u64 len = 1 << log_blocksize; + int ret; + pgoff_t mapping_index; + + ret = get_verity_mapping_index(inode, index, &mapping_index); + if (ret < 0) + return ret; + + return write_key_bytes(BTRFS_I(inode), BTRFS_VERITY_MERKLE_ITEM_KEY, + start, buf, len); +} + +const struct fsverity_operations btrfs_verityops = { + .begin_enable_verity = btrfs_begin_enable_verity, + .end_enable_verity = btrfs_end_enable_verity, + .get_verity_descriptor = btrfs_get_verity_descriptor, + .read_merkle_tree_page = btrfs_read_merkle_tree_page, + .write_merkle_tree_block = btrfs_write_merkle_tree_block, +}; diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h index 5df73001aad4..fa21c8aac78d 100644 --- a/include/uapi/linux/btrfs.h +++ b/include/uapi/linux/btrfs.h @@ -288,6 +288,7 @@ struct btrfs_ioctl_fs_info_args { * first mount when booting older kernel versions. */ #define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID (1ULL << 1) +#define BTRFS_FEATURE_COMPAT_RO_VERITY (1ULL << 2) #define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF (1ULL << 0) #define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL (1ULL << 1) @@ -308,7 +309,6 @@ struct btrfs_ioctl_fs_info_args { #define BTRFS_FEATURE_INCOMPAT_METADATA_UUID (1ULL << 10) #define BTRFS_FEATURE_INCOMPAT_RAID1C34 (1ULL << 11) #define BTRFS_FEATURE_INCOMPAT_ZONED (1ULL << 12) - struct btrfs_ioctl_feature_flags { __u64 compat_flags; __u64 compat_ro_flags; diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h index ae25280316bd..2be57416f886 100644 --- a/include/uapi/linux/btrfs_tree.h +++ b/include/uapi/linux/btrfs_tree.h @@ -118,6 +118,14 @@ #define BTRFS_INODE_REF_KEY 12 #define BTRFS_INODE_EXTREF_KEY 13 #define BTRFS_XATTR_ITEM_KEY 24 + +/* + * fsverity has a descriptor per file, and then + * a number of sha or csum items indexed by offset in to the file. + */ +#define BTRFS_VERITY_DESC_ITEM_KEY 36 +#define BTRFS_VERITY_MERKLE_ITEM_KEY 37 + #define BTRFS_ORPHAN_ITEM_KEY 48 /* reserve 2-15 close to the inode for later flexibility */ @@ -996,4 +1004,11 @@ struct btrfs_qgroup_limit_item { __le64 rsv_excl; } __attribute__ ((__packed__)); +struct btrfs_verity_descriptor_item { + /* size of the verity descriptor in bytes */ + __le64 size; + __le64 reserved[2]; + __u8 encryption; +} __attribute__ ((__packed__)); + #endif /* _BTRFS_CTREE_H_ */

[v3,2/5] btrfs: initial fsverity support

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