Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 : #include <linux/fs.h>
3 : #include <linux/fs_struct.h>
4 : #include <linux/kernel_read_file.h>
5 : #include <linux/security.h>
6 : #include <linux/vmalloc.h>
7 :
8 : /**
9 : * kernel_read_file() - read file contents into a kernel buffer
10 : *
11 : * @file file to read from
12 : * @offset where to start reading from (see below).
13 : * @buf pointer to a "void *" buffer for reading into (if
14 : * *@buf is NULL, a buffer will be allocated, and
15 : * @buf_size will be ignored)
16 : * @buf_size size of buf, if already allocated. If @buf not
17 : * allocated, this is the largest size to allocate.
18 : * @file_size if non-NULL, the full size of @file will be
19 : * written here.
20 : * @id the kernel_read_file_id identifying the type of
21 : * file contents being read (for LSMs to examine)
22 : *
23 : * @offset must be 0 unless both @buf and @file_size are non-NULL
24 : * (i.e. the caller must be expecting to read partial file contents
25 : * via an already-allocated @buf, in at most @buf_size chunks, and
26 : * will be able to determine when the entire file was read by
27 : * checking @file_size). This isn't a recommended way to read a
28 : * file, though, since it is possible that the contents might
29 : * change between calls to kernel_read_file().
30 : *
31 : * Returns number of bytes read (no single read will be bigger
32 : * than SSIZE_MAX), or negative on error.
33 : *
34 : */
35 437 : ssize_t kernel_read_file(struct file *file, loff_t offset, void **buf,
36 : size_t buf_size, size_t *file_size,
37 : enum kernel_read_file_id id)
38 : {
39 437 : loff_t i_size, pos;
40 437 : ssize_t copied;
41 437 : void *allocated = NULL;
42 437 : bool whole_file;
43 437 : int ret;
44 :
45 437 : if (offset != 0 && (!*buf || !file_size))
46 : return -EINVAL;
47 :
48 437 : if (!S_ISREG(file_inode(file)->i_mode))
49 : return -EINVAL;
50 :
51 437 : ret = deny_write_access(file);
52 437 : if (ret)
53 0 : return ret;
54 :
55 437 : i_size = i_size_read(file_inode(file));
56 437 : if (i_size <= 0) {
57 0 : ret = -EINVAL;
58 0 : goto out;
59 : }
60 : /* The file is too big for sane activities. */
61 437 : if (i_size > SSIZE_MAX) {
62 : ret = -EFBIG;
63 : goto out;
64 : }
65 : /* The entire file cannot be read in one buffer. */
66 437 : if (!file_size && offset == 0 && i_size > buf_size) {
67 0 : ret = -EFBIG;
68 0 : goto out;
69 : }
70 :
71 437 : whole_file = (offset == 0 && i_size <= buf_size);
72 437 : ret = security_kernel_read_file(file, id, whole_file);
73 437 : if (ret)
74 : goto out;
75 :
76 437 : if (file_size)
77 0 : *file_size = i_size;
78 :
79 437 : if (!*buf)
80 437 : *buf = allocated = vmalloc(i_size);
81 437 : if (!*buf) {
82 0 : ret = -ENOMEM;
83 0 : goto out;
84 : }
85 :
86 437 : pos = offset;
87 437 : copied = 0;
88 874 : while (copied < buf_size) {
89 874 : ssize_t bytes;
90 874 : size_t wanted = min_t(size_t, buf_size - copied,
91 : i_size - pos);
92 :
93 874 : bytes = kernel_read(file, *buf + copied, wanted, &pos);
94 874 : if (bytes < 0) {
95 0 : ret = bytes;
96 0 : goto out_free;
97 : }
98 :
99 874 : if (bytes == 0)
100 : break;
101 437 : copied += bytes;
102 : }
103 :
104 437 : if (whole_file) {
105 437 : if (pos != i_size) {
106 0 : ret = -EIO;
107 0 : goto out_free;
108 : }
109 :
110 : ret = security_kernel_post_read_file(file, *buf, i_size, id);
111 : }
112 :
113 0 : out_free:
114 0 : if (ret < 0) {
115 0 : if (allocated) {
116 0 : vfree(*buf);
117 0 : *buf = NULL;
118 : }
119 : }
120 :
121 0 : out:
122 437 : allow_write_access(file);
123 437 : return ret == 0 ? copied : ret;
124 : }
125 : EXPORT_SYMBOL_GPL(kernel_read_file);
126 :
127 0 : ssize_t kernel_read_file_from_path(const char *path, loff_t offset, void **buf,
128 : size_t buf_size, size_t *file_size,
129 : enum kernel_read_file_id id)
130 : {
131 0 : struct file *file;
132 0 : ssize_t ret;
133 :
134 0 : if (!path || !*path)
135 : return -EINVAL;
136 :
137 0 : file = filp_open(path, O_RDONLY, 0);
138 0 : if (IS_ERR(file))
139 0 : return PTR_ERR(file);
140 :
141 0 : ret = kernel_read_file(file, offset, buf, buf_size, file_size, id);
142 0 : fput(file);
143 0 : return ret;
144 : }
145 : EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
146 :
147 0 : ssize_t kernel_read_file_from_path_initns(const char *path, loff_t offset,
148 : void **buf, size_t buf_size,
149 : size_t *file_size,
150 : enum kernel_read_file_id id)
151 : {
152 0 : struct file *file;
153 0 : struct path root;
154 0 : ssize_t ret;
155 :
156 0 : if (!path || !*path)
157 : return -EINVAL;
158 :
159 0 : task_lock(&init_task);
160 0 : get_fs_root(init_task.fs, &root);
161 0 : task_unlock(&init_task);
162 :
163 0 : file = file_open_root(&root, path, O_RDONLY, 0);
164 0 : path_put(&root);
165 0 : if (IS_ERR(file))
166 0 : return PTR_ERR(file);
167 :
168 0 : ret = kernel_read_file(file, offset, buf, buf_size, file_size, id);
169 0 : fput(file);
170 0 : return ret;
171 : }
172 : EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);
173 :
174 0 : ssize_t kernel_read_file_from_fd(int fd, loff_t offset, void **buf,
175 : size_t buf_size, size_t *file_size,
176 : enum kernel_read_file_id id)
177 : {
178 0 : struct fd f = fdget(fd);
179 0 : ssize_t ret = -EBADF;
180 :
181 0 : if (!f.file || !(f.file->f_mode & FMODE_READ))
182 0 : goto out;
183 :
184 0 : ret = kernel_read_file(f.file, offset, buf, buf_size, file_size, id);
185 0 : out:
186 0 : fdput(f);
187 0 : return ret;
188 : }
189 : EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);
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