1e17fe657SEric Biggers // SPDX-License-Identifier: GPL-2.0-only
2e17fe657SEric Biggers /*
3e17fe657SEric Biggers * Ioctl to read verity metadata
4e17fe657SEric Biggers *
5e17fe657SEric Biggers * Copyright 2021 Google LLC
6e17fe657SEric Biggers */
7e17fe657SEric Biggers
8e17fe657SEric Biggers #include "fsverity_private.h"
9e17fe657SEric Biggers
10622699cfSEric Biggers #include <linux/backing-dev.h>
11622699cfSEric Biggers #include <linux/highmem.h>
12622699cfSEric Biggers #include <linux/sched/signal.h>
13e17fe657SEric Biggers #include <linux/uaccess.h>
14e17fe657SEric Biggers
fsverity_read_merkle_tree(struct inode * inode,const struct fsverity_info * vi,void __user * buf,u64 offset,int length)15622699cfSEric Biggers static int fsverity_read_merkle_tree(struct inode *inode,
16622699cfSEric Biggers const struct fsverity_info *vi,
17622699cfSEric Biggers void __user *buf, u64 offset, int length)
18622699cfSEric Biggers {
19622699cfSEric Biggers const struct fsverity_operations *vops = inode->i_sb->s_vop;
20622699cfSEric Biggers u64 end_offset;
21622699cfSEric Biggers unsigned int offs_in_page;
22622699cfSEric Biggers pgoff_t index, last_index;
23622699cfSEric Biggers int retval = 0;
24622699cfSEric Biggers int err = 0;
25622699cfSEric Biggers
26622699cfSEric Biggers end_offset = min(offset + length, vi->tree_params.tree_size);
27622699cfSEric Biggers if (offset >= end_offset)
28622699cfSEric Biggers return 0;
29622699cfSEric Biggers offs_in_page = offset_in_page(offset);
30622699cfSEric Biggers last_index = (end_offset - 1) >> PAGE_SHIFT;
31622699cfSEric Biggers
32622699cfSEric Biggers /*
33622699cfSEric Biggers * Iterate through each Merkle tree page in the requested range and copy
34622699cfSEric Biggers * the requested portion to userspace. Note that the Merkle tree block
35622699cfSEric Biggers * size isn't important here, as we are returning a byte stream; i.e.,
36622699cfSEric Biggers * we can just work with pages even if the tree block size != PAGE_SIZE.
37622699cfSEric Biggers */
38622699cfSEric Biggers for (index = offset >> PAGE_SHIFT; index <= last_index; index++) {
39622699cfSEric Biggers unsigned long num_ra_pages =
40622699cfSEric Biggers min_t(unsigned long, last_index - index + 1,
41622699cfSEric Biggers inode->i_sb->s_bdi->io_pages);
42622699cfSEric Biggers unsigned int bytes_to_copy = min_t(u64, end_offset - offset,
43622699cfSEric Biggers PAGE_SIZE - offs_in_page);
44622699cfSEric Biggers struct page *page;
45622699cfSEric Biggers const void *virt;
46622699cfSEric Biggers
47622699cfSEric Biggers page = vops->read_merkle_tree_page(inode, index, num_ra_pages);
48622699cfSEric Biggers if (IS_ERR(page)) {
49622699cfSEric Biggers err = PTR_ERR(page);
50622699cfSEric Biggers fsverity_err(inode,
51622699cfSEric Biggers "Error %d reading Merkle tree page %lu",
52622699cfSEric Biggers err, index);
53622699cfSEric Biggers break;
54622699cfSEric Biggers }
55622699cfSEric Biggers
568377e8a2SEric Biggers virt = kmap_local_page(page);
57622699cfSEric Biggers if (copy_to_user(buf, virt + offs_in_page, bytes_to_copy)) {
588377e8a2SEric Biggers kunmap_local(virt);
59622699cfSEric Biggers put_page(page);
60622699cfSEric Biggers err = -EFAULT;
61622699cfSEric Biggers break;
62622699cfSEric Biggers }
638377e8a2SEric Biggers kunmap_local(virt);
64622699cfSEric Biggers put_page(page);
65622699cfSEric Biggers
66622699cfSEric Biggers retval += bytes_to_copy;
67622699cfSEric Biggers buf += bytes_to_copy;
68622699cfSEric Biggers offset += bytes_to_copy;
69622699cfSEric Biggers
70622699cfSEric Biggers if (fatal_signal_pending(current)) {
71622699cfSEric Biggers err = -EINTR;
72622699cfSEric Biggers break;
73622699cfSEric Biggers }
74622699cfSEric Biggers cond_resched();
75622699cfSEric Biggers offs_in_page = 0;
76622699cfSEric Biggers }
77622699cfSEric Biggers return retval ? retval : err;
78622699cfSEric Biggers }
79947191acSEric Biggers
80947191acSEric Biggers /* Copy the requested portion of the buffer to userspace. */
fsverity_read_buffer(void __user * dst,u64 offset,int length,const void * src,size_t src_length)81947191acSEric Biggers static int fsverity_read_buffer(void __user *dst, u64 offset, int length,
82947191acSEric Biggers const void *src, size_t src_length)
83947191acSEric Biggers {
84947191acSEric Biggers if (offset >= src_length)
85947191acSEric Biggers return 0;
86947191acSEric Biggers src += offset;
87947191acSEric Biggers src_length -= offset;
88947191acSEric Biggers
89947191acSEric Biggers length = min_t(size_t, length, src_length);
90947191acSEric Biggers
91947191acSEric Biggers if (copy_to_user(dst, src, length))
92947191acSEric Biggers return -EFAULT;
93947191acSEric Biggers
94947191acSEric Biggers return length;
95947191acSEric Biggers }
96947191acSEric Biggers
fsverity_read_descriptor(struct inode * inode,void __user * buf,u64 offset,int length)97947191acSEric Biggers static int fsverity_read_descriptor(struct inode *inode,
98947191acSEric Biggers void __user *buf, u64 offset, int length)
99947191acSEric Biggers {
100947191acSEric Biggers struct fsverity_descriptor *desc;
101947191acSEric Biggers size_t desc_size;
102947191acSEric Biggers int res;
103947191acSEric Biggers
104b0487edeSZhang Jianhua res = fsverity_get_descriptor(inode, &desc);
105947191acSEric Biggers if (res)
106947191acSEric Biggers return res;
107947191acSEric Biggers
108*672d6ef4SEric Biggers /* don't include the builtin signature */
109947191acSEric Biggers desc_size = offsetof(struct fsverity_descriptor, signature);
110947191acSEric Biggers desc->sig_size = 0;
111947191acSEric Biggers
112947191acSEric Biggers res = fsverity_read_buffer(buf, offset, length, desc, desc_size);
113947191acSEric Biggers
114947191acSEric Biggers kfree(desc);
115947191acSEric Biggers return res;
116947191acSEric Biggers }
11707c99001SEric Biggers
fsverity_read_signature(struct inode * inode,void __user * buf,u64 offset,int length)11807c99001SEric Biggers static int fsverity_read_signature(struct inode *inode,
11907c99001SEric Biggers void __user *buf, u64 offset, int length)
12007c99001SEric Biggers {
12107c99001SEric Biggers struct fsverity_descriptor *desc;
12207c99001SEric Biggers int res;
12307c99001SEric Biggers
124b0487edeSZhang Jianhua res = fsverity_get_descriptor(inode, &desc);
12507c99001SEric Biggers if (res)
12607c99001SEric Biggers return res;
12707c99001SEric Biggers
12807c99001SEric Biggers if (desc->sig_size == 0) {
12907c99001SEric Biggers res = -ENODATA;
13007c99001SEric Biggers goto out;
13107c99001SEric Biggers }
13207c99001SEric Biggers
13307c99001SEric Biggers /*
134*672d6ef4SEric Biggers * Include only the builtin signature. fsverity_get_descriptor()
13507c99001SEric Biggers * already verified that sig_size is in-bounds.
13607c99001SEric Biggers */
13707c99001SEric Biggers res = fsverity_read_buffer(buf, offset, length, desc->signature,
13807c99001SEric Biggers le32_to_cpu(desc->sig_size));
13907c99001SEric Biggers out:
14007c99001SEric Biggers kfree(desc);
14107c99001SEric Biggers return res;
14207c99001SEric Biggers }
14307c99001SEric Biggers
144e17fe657SEric Biggers /**
145e17fe657SEric Biggers * fsverity_ioctl_read_metadata() - read verity metadata from a file
146e17fe657SEric Biggers * @filp: file to read the metadata from
147e17fe657SEric Biggers * @uarg: user pointer to fsverity_read_metadata_arg
148e17fe657SEric Biggers *
149e17fe657SEric Biggers * Return: length read on success, 0 on EOF, -errno on failure
150e17fe657SEric Biggers */
fsverity_ioctl_read_metadata(struct file * filp,const void __user * uarg)151e17fe657SEric Biggers int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg)
152e17fe657SEric Biggers {
153e17fe657SEric Biggers struct inode *inode = file_inode(filp);
154e17fe657SEric Biggers const struct fsverity_info *vi;
155e17fe657SEric Biggers struct fsverity_read_metadata_arg arg;
156e17fe657SEric Biggers int length;
157e17fe657SEric Biggers void __user *buf;
158e17fe657SEric Biggers
159e17fe657SEric Biggers vi = fsverity_get_info(inode);
160e17fe657SEric Biggers if (!vi)
161e17fe657SEric Biggers return -ENODATA; /* not a verity file */
162e17fe657SEric Biggers /*
163e17fe657SEric Biggers * Note that we don't have to explicitly check that the file is open for
164e17fe657SEric Biggers * reading, since verity files can only be opened for reading.
165e17fe657SEric Biggers */
166e17fe657SEric Biggers
167e17fe657SEric Biggers if (copy_from_user(&arg, uarg, sizeof(arg)))
168e17fe657SEric Biggers return -EFAULT;
169e17fe657SEric Biggers
170e17fe657SEric Biggers if (arg.__reserved)
171e17fe657SEric Biggers return -EINVAL;
172e17fe657SEric Biggers
173e17fe657SEric Biggers /* offset + length must not overflow. */
174e17fe657SEric Biggers if (arg.offset + arg.length < arg.offset)
175e17fe657SEric Biggers return -EINVAL;
176e17fe657SEric Biggers
177e17fe657SEric Biggers /* Ensure that the return value will fit in INT_MAX. */
178e17fe657SEric Biggers length = min_t(u64, arg.length, INT_MAX);
179e17fe657SEric Biggers
180e17fe657SEric Biggers buf = u64_to_user_ptr(arg.buf_ptr);
181e17fe657SEric Biggers
182e17fe657SEric Biggers switch (arg.metadata_type) {
183622699cfSEric Biggers case FS_VERITY_METADATA_TYPE_MERKLE_TREE:
184622699cfSEric Biggers return fsverity_read_merkle_tree(inode, vi, buf, arg.offset,
185622699cfSEric Biggers length);
186947191acSEric Biggers case FS_VERITY_METADATA_TYPE_DESCRIPTOR:
187947191acSEric Biggers return fsverity_read_descriptor(inode, buf, arg.offset, length);
18807c99001SEric Biggers case FS_VERITY_METADATA_TYPE_SIGNATURE:
18907c99001SEric Biggers return fsverity_read_signature(inode, buf, arg.offset, length);
190e17fe657SEric Biggers default:
191e17fe657SEric Biggers return -EINVAL;
192e17fe657SEric Biggers }
193e17fe657SEric Biggers }
194e17fe657SEric Biggers EXPORT_SYMBOL_GPL(fsverity_ioctl_read_metadata);
195