vfs: define kernel_read_file_id enumeration

To differentiate between the kernel_read_file() callers, this patch
defines a new enumeration named kernel_read_file_id and includes the
caller identifier as an argument.

Subsequent patches define READING_KEXEC_IMAGE, READING_KEXEC_INITRAMFS,
READING_FIRMWARE, READING_MODULE, and READING_POLICY.

Changelog v3:
- Replace the IMA specific enumeration with a generic one.
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Luis R. Rodriguez <mcgrof@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>

fs/exec.c

@@ -833,7 +833,7 @@ int kernel_read(struct file *file, loff_t offset,
 EXPORT_SYMBOL(kernel_read);
 
 int kernel_read_file(struct file *file, void **buf, loff_t *size,
-		     loff_t max_size)
+		     loff_t max_size, enum kernel_read_file_id id)
 {
 	loff_t i_size, pos;
 	ssize_t bytes = 0;
@@ -871,7 +871,7 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
 		goto out;
 	}
 
-	ret = security_kernel_post_read_file(file, *buf, i_size);
+	ret = security_kernel_post_read_file(file, *buf, i_size, id);
 	if (!ret)
 		*size = pos;
 

include/linux/fs.h

@@ -2576,8 +2576,13 @@ static inline void i_readcount_inc(struct inode *inode)
 #endif
 extern int do_pipe_flags(int *, int);
 
+enum kernel_read_file_id {
+	READING_MAX_ID
+};
+
 extern int kernel_read(struct file *, loff_t, char *, unsigned long);
-extern int kernel_read_file(struct file *, void **, loff_t *, loff_t);
+extern int kernel_read_file(struct file *, void **, loff_t *, loff_t,
+			    enum kernel_read_file_id);
 extern ssize_t kernel_write(struct file *, const char *, size_t, loff_t);
 extern ssize_t __kernel_write(struct file *, const char *, size_t, loff_t *);
 extern struct file * open_exec(const char *);

include/linux/lsm_hooks.h

@@ -567,6 +567,7 @@
  *	by the kernel.
  *	@buf pointer to buffer containing the file contents.
  *	@size length of the file contents.
+ *	@id kernel read file identifier
  *	Return 0 if permission is granted.
  * @task_fix_setuid:
  *	Update the module's state after setting one or more of the user
@@ -1464,7 +1465,8 @@ union security_list_options {
 	int (*kernel_fw_from_file)(struct file *file, char *buf, size_t size);
 	int (*kernel_module_request)(char *kmod_name);
 	int (*kernel_module_from_file)(struct file *file);
-	int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size);
+	int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size,
+				     enum kernel_read_file_id id);
 	int (*task_fix_setuid)(struct cred *new, const struct cred *old,
 				int flags);
 	int (*task_setpgid)(struct task_struct *p, pid_t pgid);

include/linux/security.h

@@ -28,6 +28,7 @@
 #include <linux/err.h>
 #include <linux/string.h>
 #include <linux/mm.h>
+#include <linux/fs.h>
 
 struct linux_binprm;
 struct cred;
@@ -301,7 +302,8 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode);
 int security_kernel_fw_from_file(struct file *file, char *buf, size_t size);
 int security_kernel_module_request(char *kmod_name);
 int security_kernel_module_from_file(struct file *file);
-int security_kernel_post_read_file(struct file *file, char *buf, loff_t size);
+int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
+				   enum kernel_read_file_id id);
 int security_task_fix_setuid(struct cred *new, const struct cred *old,
 			     int flags);
 int security_task_setpgid(struct task_struct *p, pid_t pgid);
@@ -868,7 +870,8 @@ static inline int security_kernel_module_from_file(struct file *file)
 }
 
 static inline int security_kernel_post_read_file(struct file *file,
-						 char *buf, loff_t size)
+						 char *buf, loff_t size,
+						 enum kernel_read_file_id id)
 {
 	return 0;
 }

security/security.c

@@ -910,9 +910,10 @@ int security_kernel_module_from_file(struct file *file)
 	return ima_module_check(file);
 }
 
-int security_kernel_post_read_file(struct file *file, char *buf, loff_t size)
+int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
+				   enum kernel_read_file_id id)
 {
-	return call_int_hook(kernel_post_read_file, 0, file, buf, size);
+	return call_int_hook(kernel_post_read_file, 0, file, buf, size, id);
 }
 EXPORT_SYMBOL_GPL(security_kernel_post_read_file);