exec: Remove do_execve_file

Now that the last callser has been removed remove this code from exec.

For anyone thinking of resurrecing do_execve_file please note that
the code was buggy in several fundamental ways.

- It did not ensure the file it was passed was read-only and that
deny_write_access had been called on it. Which subtlely breaks
invaniants in exec.

- The caller of do_execve_file was expected to hold and put a
reference to the file, but an extra reference for use by exec was
not taken so that when exec put it's reference to the file an
underflow occured on the file reference count.

- The point of the interface was so that a pathname did not need to
exist. Which breaks pathname based LSMs.

Tetsuo Handa originally reported these issues[1]. While it was clear
that deny_write_access was missing the fundamental incompatibility
with the passed in O_RDWR filehandle was not immediately recognized.

All of these issues were fixed by modifying the usermode driver code
to have a path, so it did not need this hack.

Reported-by: Tetsuo Handa <[e-mail]>
[1] https://lore.kernel.org/linux-fsdevel/[e-mail]/
v1: https://lkml.kernel.org/r/[e-mail]
v2: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Reviewed-by: Greg Kroah-Hartman <[e-mail]>
Acked-by: Alexei Starovoitov <[e-mail]>
Tested-by: Alexei Starovoitov <[e-mail]>
Signed-off-by: "Eric W. Biederman" <[e-mail]>

fs/exec.c

···
 /*
  * sys_execve() executes a new program.
  */
-static int __do_execve_file(int fd, struct filename *filename,
-			    struct user_arg_ptr argv,
-			    struct user_arg_ptr envp,
-			    int flags, struct file *file)
+static int do_execveat_common(int fd, struct filename *filename,
+			      struct user_arg_ptr argv,
+			      struct user_arg_ptr envp,
+			      int flags)
 {
 	char *pathbuf = NULL;
 	struct linux_binprm *bprm;
+	struct file *file;
 	struct files_struct *displaced;
 	int retval;
 
···
 	check_unsafe_exec(bprm);
 	current->in_execve = 1;
 
-	if (!file)
-		file = do_open_execat(fd, filename, flags);
+	file = do_open_execat(fd, filename, flags);
 	retval = PTR_ERR(file);
 	if (IS_ERR(file))
 		goto out_unmark;
···
 	sched_exec();
 
 	bprm->file = file;
-	if (!filename) {
-		bprm->filename = "none";
-	} else if (fd == AT_FDCWD || filename->name[0] == '/') {
+	if (fd == AT_FDCWD || filename->name[0] == '/') {
 		bprm->filename = filename->name;
 	} else {
 		if (filename->name[0] == '\0')
···
 	task_numa_free(current, false);
 	free_bprm(bprm);
 	kfree(pathbuf);
-	if (filename)
-		putname(filename);
+	putname(filename);
 	if (displaced)
 		put_files_struct(displaced);
 	return retval;
···
 	if (displaced)
 		reset_files_struct(displaced);
 out_ret:
-	if (filename)
-		putname(filename);
+	putname(filename);
 	return retval;
-}
-
-static int do_execveat_common(int fd, struct filename *filename,
-			      struct user_arg_ptr argv,
-			      struct user_arg_ptr envp,
-			      int flags)
-{
-	return __do_execve_file(fd, filename, argv, envp, flags, NULL);
-}
-
-int do_execve_file(struct file *file, void *__argv, void *__envp)
-{
-	struct user_arg_ptr argv = { .ptr.native = __argv };
-	struct user_arg_ptr envp = { .ptr.native = __envp };
-
-	return __do_execve_file(AT_FDCWD, NULL, argv, envp, 0, file);
 }
 
 int do_execve(struct filename *filename,

include/linux/binfmts.h

···
 		       const char __user * const __user *,
 		       const char __user * const __user *,
 		       int);
-int do_execve_file(struct file *file, void *__argv, void *__envp);
 
 #endif /* _LINUX_BINFMTS_H */