exec: binfmt_misc: remove the confusing e->interp_file != NULL checks

If MISC_FMT_OPEN_FILE flag is set e->interp_file must be valid or we
have a bug which should not be silently ignored.

Link: http://lkml.kernel.org/r/20170922143647.GA17222@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ben Woodard <woodard@redhat.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jim Foraker <foraker1@llnl.gov>
Cc: <tdhooge@llnl.gov>
Cc: Travis Gummels <tgummels@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/binfmt_misc.c

@@ -205,7 +205,7 @@ static int load_misc_binary(struct linux_binprm *bprm)
 	if (retval < 0)
 		goto error;
 
-	if (fmt->flags & MISC_FMT_OPEN_FILE && fmt->interp_file) {
+	if (fmt->flags & MISC_FMT_OPEN_FILE) {
 		interp_file = filp_clone_open(fmt->interp_file);
 		if (!IS_ERR(interp_file))
 			deny_write_access(interp_file);
@@ -596,7 +596,7 @@ static void bm_evict_inode(struct inode *inode)
 {
 	Node *e = inode->i_private;
 
-	if ((e->flags & MISC_FMT_OPEN_FILE) && e->interp_file)
+	if (e->flags & MISC_FMT_OPEN_FILE)
 		filp_close(e->interp_file, NULL);
 
 	clear_inode(inode);