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 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 loff_t i_size, pos; 40 ssize_t copied; 41 void *allocated = NULL; 42 bool whole_file; 43 int ret; 44 45 if (offset != 0 && (!*buf || !file_size)) 46 return -EINVAL; 47 48 if (!S_ISREG(file_inode(file)->i_mode)) 49 return -EINVAL; 50 51 ret = deny_write_access(file); 52 if (ret) 53 return ret; 54 55 i_size = i_size_read(file_inode(file)); 56 if (i_size <= 0) { 57 ret = -EINVAL; 58 goto out; 59 } 60 /* The file is too big for sane activities. */ 61 if (i_size > SSIZE_MAX) { 62 ret = -EFBIG; 63 goto out; 64 } 65 /* The entire file cannot be read in one buffer. */ 66 if (!file_size && offset == 0 && i_size > buf_size) { 67 ret = -EFBIG; 68 goto out; 69 } 70 71 whole_file = (offset == 0 && i_size <= buf_size); 72 ret = security_kernel_read_file(file, id, whole_file); 73 if (ret) 74 goto out; 75 76 if (file_size) 77 *file_size = i_size; 78 79 if (!*buf) 80 *buf = allocated = vmalloc(i_size); 81 if (!*buf) { 82 ret = -ENOMEM; 83 goto out; 84 } 85 86 pos = offset; 87 copied = 0; 88 while (copied < buf_size) { 89 ssize_t bytes; 90 size_t wanted = min_t(size_t, buf_size - copied, 91 i_size - pos); 92 93 bytes = kernel_read(file, *buf + copied, wanted, &pos); 94 if (bytes < 0) { 95 ret = bytes; 96 goto out_free; 97 } 98 99 if (bytes == 0) 100 break; 101 copied += bytes; 102 } 103 104 if (whole_file) { 105 if (pos != i_size) { 106 ret = -EIO; 107 goto out_free; 108 } 109 110 ret = security_kernel_post_read_file(file, *buf, i_size, id); 111 } 112 113 out_free: 114 if (ret < 0) { 115 if (allocated) { 116 vfree(*buf); 117 *buf = NULL; 118 } 119 } 120 121 out: 122 allow_write_access(file); 123 return ret == 0 ? copied : ret; 124 } 125 EXPORT_SYMBOL_GPL(kernel_read_file); 126 127 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 struct file *file; 132 ssize_t ret; 133 134 if (!path || !*path) 135 return -EINVAL; 136 137 file = filp_open(path, O_RDONLY, 0); 138 if (IS_ERR(file)) 139 return PTR_ERR(file); 140 141 ret = kernel_read_file(file, offset, buf, buf_size, file_size, id); 142 fput(file); 143 return ret; 144 } 145 EXPORT_SYMBOL_GPL(kernel_read_file_from_path); 146 147 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 struct file *file; 153 struct path root; 154 ssize_t ret; 155 156 if (!path || !*path) 157 return -EINVAL; 158 159 task_lock(&init_task); 160 get_fs_root(init_task.fs, &root); 161 task_unlock(&init_task); 162 163 file = file_open_root(&root, path, O_RDONLY, 0); 164 path_put(&root); 165 if (IS_ERR(file)) 166 return PTR_ERR(file); 167 168 ret = kernel_read_file(file, offset, buf, buf_size, file_size, id); 169 fput(file); 170 return ret; 171 } 172 EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns); 173 174 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 struct fd f = fdget(fd); 179 ssize_t ret = -EBADF; 180 181 if (!f.file || !(f.file->f_mode & FMODE_READ)) 182 goto out; 183 184 ret = kernel_read_file(f.file, offset, buf, buf_size, file_size, id); 185 out: 186 fdput(f); 187 return ret; 188 } 189 EXPORT_SYMBOL_GPL(kernel_read_file_from_fd); 190