diff options
Diffstat (limited to 'fs/verity/read_metadata.c')
| -rw-r--r-- | fs/verity/read_metadata.c | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c new file mode 100644 index 0000000000..f58432772d --- /dev/null +++ b/fs/verity/read_metadata.c @@ -0,0 +1,194 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Ioctl to read verity metadata + * + * Copyright 2021 Google LLC + */ + +#include "fsverity_private.h" + +#include <linux/backing-dev.h> +#include <linux/highmem.h> +#include <linux/sched/signal.h> +#include <linux/uaccess.h> + +static int fsverity_read_merkle_tree(struct inode *inode, + const struct fsverity_info *vi, + void __user *buf, u64 offset, int length) +{ + const struct fsverity_operations *vops = inode->i_sb->s_vop; + u64 end_offset; + unsigned int offs_in_page; + pgoff_t index, last_index; + int retval = 0; + int err = 0; + + end_offset = min(offset + length, vi->tree_params.tree_size); + if (offset >= end_offset) + return 0; + offs_in_page = offset_in_page(offset); + last_index = (end_offset - 1) >> PAGE_SHIFT; + + /* + * Iterate through each Merkle tree page in the requested range and copy + * the requested portion to userspace. Note that the Merkle tree block + * size isn't important here, as we are returning a byte stream; i.e., + * we can just work with pages even if the tree block size != PAGE_SIZE. + */ + for (index = offset >> PAGE_SHIFT; index <= last_index; index++) { + unsigned long num_ra_pages = + min_t(unsigned long, last_index - index + 1, + inode->i_sb->s_bdi->io_pages); + unsigned int bytes_to_copy = min_t(u64, end_offset - offset, + PAGE_SIZE - offs_in_page); + struct page *page; + const void *virt; + + page = vops->read_merkle_tree_page(inode, index, num_ra_pages); + if (IS_ERR(page)) { + err = PTR_ERR(page); + fsverity_err(inode, + "Error %d reading Merkle tree page %lu", + err, index); + break; + } + + virt = kmap_local_page(page); + if (copy_to_user(buf, virt + offs_in_page, bytes_to_copy)) { + kunmap_local(virt); + put_page(page); + err = -EFAULT; + break; + } + kunmap_local(virt); + put_page(page); + + retval += bytes_to_copy; + buf += bytes_to_copy; + offset += bytes_to_copy; + + if (fatal_signal_pending(current)) { + err = -EINTR; + break; + } + cond_resched(); + offs_in_page = 0; + } + return retval ? retval : err; +} + +/* Copy the requested portion of the buffer to userspace. */ +static int fsverity_read_buffer(void __user *dst, u64 offset, int length, + const void *src, size_t src_length) +{ + if (offset >= src_length) + return 0; + src += offset; + src_length -= offset; + + length = min_t(size_t, length, src_length); + + if (copy_to_user(dst, src, length)) + return -EFAULT; + + return length; +} + +static int fsverity_read_descriptor(struct inode *inode, + void __user *buf, u64 offset, int length) +{ + struct fsverity_descriptor *desc; + size_t desc_size; + int res; + + res = fsverity_get_descriptor(inode, &desc); + if (res) + return res; + + /* don't include the builtin signature */ + desc_size = offsetof(struct fsverity_descriptor, signature); + desc->sig_size = 0; + + res = fsverity_read_buffer(buf, offset, length, desc, desc_size); + + kfree(desc); + return res; +} + +static int fsverity_read_signature(struct inode *inode, + void __user *buf, u64 offset, int length) +{ + struct fsverity_descriptor *desc; + int res; + + res = fsverity_get_descriptor(inode, &desc); + if (res) + return res; + + if (desc->sig_size == 0) { + res = -ENODATA; + goto out; + } + + /* + * Include only the builtin signature. fsverity_get_descriptor() + * already verified that sig_size is in-bounds. + */ + res = fsverity_read_buffer(buf, offset, length, desc->signature, + le32_to_cpu(desc->sig_size)); +out: + kfree(desc); + return res; +} + +/** + * fsverity_ioctl_read_metadata() - read verity metadata from a file + * @filp: file to read the metadata from + * @uarg: user pointer to fsverity_read_metadata_arg + * + * Return: length read on success, 0 on EOF, -errno on failure + */ +int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) +{ + struct inode *inode = file_inode(filp); + const struct fsverity_info *vi; + struct fsverity_read_metadata_arg arg; + int length; + void __user *buf; + + vi = fsverity_get_info(inode); + if (!vi) + return -ENODATA; /* not a verity file */ + /* + * Note that we don't have to explicitly check that the file is open for + * reading, since verity files can only be opened for reading. + */ + + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + + if (arg.__reserved) + return -EINVAL; + + /* offset + length must not overflow. */ + if (arg.offset + arg.length < arg.offset) + return -EINVAL; + + /* Ensure that the return value will fit in INT_MAX. */ + length = min_t(u64, arg.length, INT_MAX); + + buf = u64_to_user_ptr(arg.buf_ptr); + + switch (arg.metadata_type) { + case FS_VERITY_METADATA_TYPE_MERKLE_TREE: + return fsverity_read_merkle_tree(inode, vi, buf, arg.offset, + length); + case FS_VERITY_METADATA_TYPE_DESCRIPTOR: + return fsverity_read_descriptor(inode, buf, arg.offset, length); + case FS_VERITY_METADATA_TYPE_SIGNATURE: + return fsverity_read_signature(inode, buf, arg.offset, length); + default: + return -EINVAL; + } +} +EXPORT_SYMBOL_GPL(fsverity_ioctl_read_metadata); |