1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Ioctl to read verity metadata
4 *
5 * Copyright 2021 Google LLC
6 */
7
8 #include "fsverity_private.h"
9
10 #include <linux/backing-dev.h>
11 #include <linux/highmem.h>
12 #include <linux/sched/signal.h>
13 #include <linux/uaccess.h>
14
fsverity_read_merkle_tree(struct inode * inode,const struct fsverity_info * vi,void __user * buf,u64 offset,int length)15 static int fsverity_read_merkle_tree(struct inode *inode,
16 const struct fsverity_info *vi,
17 void __user *buf, u64 offset, int length)
18 {
19 const struct fsverity_operations *vops = inode->i_sb->s_vop;
20 u64 end_offset;
21 unsigned int offs_in_page;
22 pgoff_t index, last_index;
23 int retval = 0;
24 int err = 0;
25
26 end_offset = min(offset + length, vi->tree_params.tree_size);
27 if (offset >= end_offset)
28 return 0;
29 offs_in_page = offset_in_page(offset);
30 last_index = (end_offset - 1) >> PAGE_SHIFT;
31
32 /*
33 * Iterate through each Merkle tree page in the requested range and copy
34 * the requested portion to userspace. Note that the Merkle tree block
35 * size isn't important here, as we are returning a byte stream; i.e.,
36 * we can just work with pages even if the tree block size != PAGE_SIZE.
37 */
38 for (index = offset >> PAGE_SHIFT; index <= last_index; index++) {
39 unsigned long num_ra_pages =
40 min_t(unsigned long, last_index - index + 1,
41 inode->i_sb->s_bdi->io_pages);
42 unsigned int bytes_to_copy = min_t(u64, end_offset - offset,
43 PAGE_SIZE - offs_in_page);
44 struct page *page;
45 const void *virt;
46
47 page = vops->read_merkle_tree_page(inode, index, num_ra_pages);
48 if (IS_ERR(page)) {
49 err = PTR_ERR(page);
50 fsverity_err(inode,
51 "Error %d reading Merkle tree page %lu",
52 err, index);
53 break;
54 }
55
56 virt = kmap(page);
57 if (copy_to_user(buf, virt + offs_in_page, bytes_to_copy)) {
58 kunmap(page);
59 put_page(page);
60 err = -EFAULT;
61 break;
62 }
63 kunmap(page);
64 put_page(page);
65
66 retval += bytes_to_copy;
67 buf += bytes_to_copy;
68 offset += bytes_to_copy;
69
70 if (fatal_signal_pending(current)) {
71 err = -EINTR;
72 break;
73 }
74 cond_resched();
75 offs_in_page = 0;
76 }
77 return retval ? retval : err;
78 }
79
80 /* 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)81 static int fsverity_read_buffer(void __user *dst, u64 offset, int length,
82 const void *src, size_t src_length)
83 {
84 if (offset >= src_length)
85 return 0;
86 src += offset;
87 src_length -= offset;
88
89 length = min_t(size_t, length, src_length);
90
91 if (copy_to_user(dst, src, length))
92 return -EFAULT;
93
94 return length;
95 }
96
fsverity_read_descriptor(struct inode * inode,void __user * buf,u64 offset,int length)97 static int fsverity_read_descriptor(struct inode *inode,
98 void __user *buf, u64 offset, int length)
99 {
100 struct fsverity_descriptor *desc;
101 size_t desc_size;
102 int res;
103
104 res = fsverity_get_descriptor(inode, &desc, &desc_size);
105 if (res)
106 return res;
107
108 /* don't include the signature */
109 desc_size = offsetof(struct fsverity_descriptor, signature);
110 desc->sig_size = 0;
111
112 res = fsverity_read_buffer(buf, offset, length, desc, desc_size);
113
114 kfree(desc);
115 return res;
116 }
117
fsverity_read_signature(struct inode * inode,void __user * buf,u64 offset,int length)118 static int fsverity_read_signature(struct inode *inode,
119 void __user *buf, u64 offset, int length)
120 {
121 struct fsverity_descriptor *desc;
122 size_t desc_size;
123 int res;
124
125 res = fsverity_get_descriptor(inode, &desc, &desc_size);
126 if (res)
127 return res;
128
129 if (desc->sig_size == 0) {
130 res = -ENODATA;
131 goto out;
132 }
133
134 /*
135 * Include only the signature. Note that fsverity_get_descriptor()
136 * already verified that sig_size is in-bounds.
137 */
138 res = fsverity_read_buffer(buf, offset, length, desc->signature,
139 le32_to_cpu(desc->sig_size));
140 out:
141 kfree(desc);
142 return res;
143 }
144
145 /**
146 * fsverity_ioctl_read_metadata() - read verity metadata from a file
147 * @filp: file to read the metadata from
148 * @uarg: user pointer to fsverity_read_metadata_arg
149 *
150 * Return: length read on success, 0 on EOF, -errno on failure
151 */
fsverity_ioctl_read_metadata(struct file * filp,const void __user * uarg)152 int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg)
153 {
154 struct inode *inode = file_inode(filp);
155 const struct fsverity_info *vi;
156 struct fsverity_read_metadata_arg arg;
157 int length;
158 void __user *buf;
159
160 vi = fsverity_get_info(inode);
161 if (!vi)
162 return -ENODATA; /* not a verity file */
163 /*
164 * Note that we don't have to explicitly check that the file is open for
165 * reading, since verity files can only be opened for reading.
166 */
167
168 if (copy_from_user(&arg, uarg, sizeof(arg)))
169 return -EFAULT;
170
171 if (arg.__reserved)
172 return -EINVAL;
173
174 /* offset + length must not overflow. */
175 if (arg.offset + arg.length < arg.offset)
176 return -EINVAL;
177
178 /* Ensure that the return value will fit in INT_MAX. */
179 length = min_t(u64, arg.length, INT_MAX);
180
181 buf = u64_to_user_ptr(arg.buf_ptr);
182
183 switch (arg.metadata_type) {
184 case FS_VERITY_METADATA_TYPE_MERKLE_TREE:
185 return fsverity_read_merkle_tree(inode, vi, buf, arg.offset,
186 length);
187 case FS_VERITY_METADATA_TYPE_DESCRIPTOR:
188 return fsverity_read_descriptor(inode, buf, arg.offset, length);
189 case FS_VERITY_METADATA_TYPE_SIGNATURE:
190 return fsverity_read_signature(inode, buf, arg.offset, length);
191 default:
192 return -EINVAL;
193 }
194 }
195 EXPORT_SYMBOL_GPL(fsverity_ioctl_read_metadata);
196