fs/kernel_read_file: Add file_size output argument

In preparation for adding partial read support, add an optional output
argument to kernel_read_file*() that reports the file size so callers
can reason more easily about their reading progress.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Scott Branden <scott.branden@broadcom.com>
Link: https://lore.kernel.org/r/20201002173828.2099543-8-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/firmware_loader/main.c

@@ -500,6 +500,7 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
 
 		/* load firmware files from the mount namespace of init */
 		rc = kernel_read_file_from_path_initns(path, &buffer, msize,
+						       NULL,
 						       READING_FIRMWARE);
 		if (rc < 0) {
 			if (rc != -ENOENT)

fs/kernel_read_file.c

@@ -14,6 +14,8 @@
  *		@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)
  *
@@ -22,7 +24,8 @@
  *
  */
 int kernel_read_file(struct file *file, void **buf,
-		     size_t buf_size, enum kernel_read_file_id id)
+		     size_t buf_size, size_t *file_size,
+		     enum kernel_read_file_id id)
 {
 	loff_t i_size, pos;
 	ssize_t bytes = 0;
@@ -49,6 +52,8 @@ int kernel_read_file(struct file *file, void **buf,
 		ret = -EFBIG;
 		goto out;
 	}
+	if (file_size)
+		*file_size = i_size;
 
 	if (!*buf)
 		*buf = allocated = vmalloc(i_size);
@@ -91,7 +96,8 @@ out:
 EXPORT_SYMBOL_GPL(kernel_read_file);
 
 int kernel_read_file_from_path(const char *path, void **buf,
-			       size_t buf_size, enum kernel_read_file_id id)
+			       size_t buf_size, size_t *file_size,
+			       enum kernel_read_file_id id)
 {
 	struct file *file;
 	int ret;
@@ -103,14 +109,14 @@ int kernel_read_file_from_path(const char *path, void **buf,
 	if (IS_ERR(file))
 		return PTR_ERR(file);
 
-	ret = kernel_read_file(file, buf, buf_size, id);
+	ret = kernel_read_file(file, 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, void **buf,
-				      size_t buf_size,
+				      size_t buf_size, size_t *file_size,
 				      enum kernel_read_file_id id)
 {
 	struct file *file;
@@ -129,13 +135,14 @@ int kernel_read_file_from_path_initns(const char *path, void **buf,
 	if (IS_ERR(file))
 		return PTR_ERR(file);
 
-	ret = kernel_read_file(file, buf, buf_size, id);
+	ret = kernel_read_file(file, 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, void **buf, size_t buf_size,
+			     size_t *file_size,
 			     enum kernel_read_file_id id)
 {
 	struct fd f = fdget(fd);
@@ -144,7 +151,7 @@ int kernel_read_file_from_fd(int fd, void **buf, size_t buf_size,
 	if (!f.file)
 		goto out;
 
-	ret = kernel_read_file(f.file, buf, buf_size, id);
+	ret = kernel_read_file(f.file, buf, buf_size, file_size, id);
 out:
 	fdput(f);
 	return ret;

include/linux/kernel_read_file.h

@@ -37,15 +37,19 @@ static inline const char *kernel_read_file_id_str(enum kernel_read_file_id id)
 
 int kernel_read_file(struct file *file,
 		     void **buf, size_t buf_size,
+		     size_t *file_size,
 		     enum kernel_read_file_id id);
 int kernel_read_file_from_path(const char *path,
 			       void **buf, size_t buf_size,
+			       size_t *file_size,
 			       enum kernel_read_file_id id);
 int kernel_read_file_from_path_initns(const char *path,
 				      void **buf, size_t buf_size,
+				      size_t *file_size,
 				      enum kernel_read_file_id id);
 int kernel_read_file_from_fd(int fd,
 			     void **buf, size_t buf_size,
+			     size_t *file_size,
 			     enum kernel_read_file_id id);
 
 #endif /* _LINUX_KERNEL_READ_FILE_H */

kernel/kexec_file.c

@@ -222,7 +222,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 	void *ldata;
 
 	ret = kernel_read_file_from_fd(kernel_fd, &image->kernel_buf,
-				       INT_MAX, READING_KEXEC_IMAGE);
+				       INT_MAX, NULL, READING_KEXEC_IMAGE);
 	if (ret < 0)
 		return ret;
 	image->kernel_buf_len = ret;
@@ -242,7 +242,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 	/* It is possible that there no initramfs is being loaded */
 	if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
 		ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf,
-					       INT_MAX,
+					       INT_MAX, NULL,
 					       READING_KEXEC_INITRAMFS);
 		if (ret < 0)
 			goto out;

kernel/module.c

@@ -4048,7 +4048,7 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
 		      |MODULE_INIT_IGNORE_VERMAGIC))
 		return -EINVAL;
 
-	err = kernel_read_file_from_fd(fd, &hdr, INT_MAX,
+	err = kernel_read_file_from_fd(fd, &hdr, INT_MAX, NULL,
 				       READING_MODULE);
 	if (err < 0)
 		return err;

security/integrity/digsig.c

@@ -175,7 +175,7 @@ int __init integrity_load_x509(const unsigned int id, const char *path)
 	int rc;
 	key_perm_t perm;
 
-	rc = kernel_read_file_from_path(path, &data, INT_MAX,
+	rc = kernel_read_file_from_path(path, &data, INT_MAX, NULL,
 					READING_X509_CERTIFICATE);
 	if (rc < 0) {
 		pr_err("Unable to open file: %s (%d)", path, rc);

security/integrity/ima/ima_fs.c

@@ -284,7 +284,7 @@ static ssize_t ima_read_policy(char *path)
 	datap = path;
 	strsep(&datap, "\n");
 
-	rc = kernel_read_file_from_path(path, &data, INT_MAX, READING_POLICY);
+	rc = kernel_read_file_from_path(path, &data, INT_MAX, NULL, READING_POLICY);
 	if (rc < 0) {
 		pr_err("Unable to open file: %s (%d)", path, rc);
 		return rc;