fs/kernel_read_file: Split into separate source file
These routines are used in places outside of exec(2), so in preparation
for refactoring them, move them into a separate source file,
fs/kernel_read_file.c.
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Acked-by: Scott Branden <scott.branden@broadcom.com>
Link: https://lore.kernel.org/r/20201002173828.2099543-5-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/kernel_read_file.c b/fs/kernel_read_file.c
new file mode 100644
index 0000000..54d972d
--- /dev/null
+++ b/fs/kernel_read_file.c
@@ -0,0 +1,138 @@
+// 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>
+
+int kernel_read_file(struct file *file, void **buf, loff_t *size,
+ loff_t max_size, enum kernel_read_file_id id)
+{
+ loff_t i_size, pos;
+ ssize_t bytes = 0;
+ void *allocated = NULL;
+ int ret;
+
+ if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
+ return -EINVAL;
+
+ ret = deny_write_access(file);
+ if (ret)
+ return ret;
+
+ ret = security_kernel_read_file(file, id);
+ if (ret)
+ goto out;
+
+ i_size = i_size_read(file_inode(file));
+ if (i_size <= 0) {
+ ret = -EINVAL;
+ goto out;
+ }
+ if (i_size > SIZE_MAX || (max_size > 0 && i_size > max_size)) {
+ ret = -EFBIG;
+ goto out;
+ }
+
+ if (!*buf)
+ *buf = allocated = vmalloc(i_size);
+ if (!*buf) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ pos = 0;
+ while (pos < i_size) {
+ bytes = kernel_read(file, *buf + pos, i_size - pos, &pos);
+ if (bytes < 0) {
+ ret = bytes;
+ goto out_free;
+ }
+
+ if (bytes == 0)
+ break;
+ }
+
+ if (pos != i_size) {
+ ret = -EIO;
+ goto out_free;
+ }
+
+ ret = security_kernel_post_read_file(file, *buf, i_size, id);
+ if (!ret)
+ *size = pos;
+
+out_free:
+ if (ret < 0) {
+ if (allocated) {
+ vfree(*buf);
+ *buf = NULL;
+ }
+ }
+
+out:
+ allow_write_access(file);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kernel_read_file);
+
+int kernel_read_file_from_path(const char *path, void **buf, loff_t *size,
+ loff_t max_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, buf, size, max_size, id);
+ fput(file);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
+
+int kernel_read_file_from_path_initns(const char *path, void **buf,
+ loff_t *size, loff_t max_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, buf, size, max_size, id);
+ fput(file);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);
+
+int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
+ enum kernel_read_file_id id)
+{
+ struct fd f = fdget(fd);
+ int ret = -EBADF;
+
+ if (!f.file)
+ goto out;
+
+ ret = kernel_read_file(f.file, buf, size, max_size, id);
+out:
+ fdput(f);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);