diff options
Diffstat (limited to 'fs/kernel_read_file.c')
| -rw-r--r-- | fs/kernel_read_file.c | 189 |
1 files changed, 189 insertions, 0 deletions
diff --git a/fs/kernel_read_file.c b/fs/kernel_read_file.c new file mode 100644 index 000000000..c84d87f55 --- /dev/null +++ b/fs/kernel_read_file.c @@ -0,0 +1,189 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <linux/fs.h> +#include <linux/fs_struct.h> +#include <linux/kernel_read_file.h> +#include <linux/security.h> +#include <linux/vmalloc.h> + +/** + * kernel_read_file() - read file contents into a kernel buffer + * + * @file file to read from + * @offset where to start reading from (see below). + * @buf pointer to a "void *" buffer for reading into (if + * *@buf is NULL, a buffer will be allocated, and + * @buf_size will be ignored) + * @buf_size size of buf, if already allocated. If @buf not + * allocated, this is the largest size to allocate. + * @file_size if non-NULL, the full size of @file will be + * written here. + * @id the kernel_read_file_id identifying the type of + * file contents being read (for LSMs to examine) + * + * @offset must be 0 unless both @buf and @file_size are non-NULL + * (i.e. the caller must be expecting to read partial file contents + * via an already-allocated @buf, in at most @buf_size chunks, and + * will be able to determine when the entire file was read by + * checking @file_size). This isn't a recommended way to read a + * file, though, since it is possible that the contents might + * change between calls to kernel_read_file(). + * + * Returns number of bytes read (no single read will be bigger + * than INT_MAX), or negative on error. + * + */ +int kernel_read_file(struct file *file, loff_t offset, void **buf, + size_t buf_size, size_t *file_size, + enum kernel_read_file_id id) +{ + loff_t i_size, pos; + size_t copied; + void *allocated = NULL; + bool whole_file; + int ret; + + if (offset != 0 && (!*buf || !file_size)) + return -EINVAL; + + if (!S_ISREG(file_inode(file)->i_mode)) + return -EINVAL; + + ret = deny_write_access(file); + if (ret) + return ret; + + i_size = i_size_read(file_inode(file)); + if (i_size <= 0) { + ret = -EINVAL; + goto out; + } + /* The file is too big for sane activities. */ + if (i_size > INT_MAX) { + ret = -EFBIG; + goto out; + } + /* The entire file cannot be read in one buffer. */ + if (!file_size && offset == 0 && i_size > buf_size) { + ret = -EFBIG; + goto out; + } + + whole_file = (offset == 0 && i_size <= buf_size); + ret = security_kernel_read_file(file, id, whole_file); + if (ret) + goto out; + + if (file_size) + *file_size = i_size; + + if (!*buf) + *buf = allocated = vmalloc(i_size); + if (!*buf) { + ret = -ENOMEM; + goto out; + } + + pos = offset; + copied = 0; + while (copied < buf_size) { + ssize_t bytes; + size_t wanted = min_t(size_t, buf_size - copied, + i_size - pos); + + bytes = kernel_read(file, *buf + copied, wanted, &pos); + if (bytes < 0) { + ret = bytes; + goto out_free; + } + + if (bytes == 0) + break; + copied += bytes; + } + + if (whole_file) { + if (pos != i_size) { + ret = -EIO; + goto out_free; + } + + ret = security_kernel_post_read_file(file, *buf, i_size, id); + } + +out_free: + if (ret < 0) { + if (allocated) { + vfree(*buf); + *buf = NULL; + } + } + +out: + allow_write_access(file); + return ret == 0 ? copied : ret; +} +EXPORT_SYMBOL_GPL(kernel_read_file); + +int kernel_read_file_from_path(const char *path, loff_t offset, void **buf, + size_t buf_size, size_t *file_size, + enum kernel_read_file_id id) +{ + struct file *file; + int ret; + + if (!path || !*path) + return -EINVAL; + + file = filp_open(path, O_RDONLY, 0); + if (IS_ERR(file)) + return PTR_ERR(file); + + ret = kernel_read_file(file, offset, buf, buf_size, file_size, id); + fput(file); + return ret; +} +EXPORT_SYMBOL_GPL(kernel_read_file_from_path); + +int kernel_read_file_from_path_initns(const char *path, loff_t offset, + void **buf, size_t buf_size, + size_t *file_size, + enum kernel_read_file_id id) +{ + struct file *file; + struct path root; + int ret; + + if (!path || !*path) + return -EINVAL; + + task_lock(&init_task); + get_fs_root(init_task.fs, &root); + task_unlock(&init_task); + + file = file_open_root(root.dentry, root.mnt, path, O_RDONLY, 0); + path_put(&root); + if (IS_ERR(file)) + return PTR_ERR(file); + + ret = kernel_read_file(file, offset, buf, buf_size, file_size, id); + fput(file); + return ret; +} +EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns); + +int kernel_read_file_from_fd(int fd, loff_t offset, void **buf, + size_t buf_size, size_t *file_size, + enum kernel_read_file_id id) +{ + struct fd f = fdget(fd); + int ret = -EBADF; + + if (!f.file || !(f.file->f_mode & FMODE_READ)) + goto out; + + ret = kernel_read_file(f.file, offset, buf, buf_size, file_size, id); +out: + fdput(f); + return ret; +} +EXPORT_SYMBOL_GPL(kernel_read_file_from_fd); |