exec: cleanup the CONFIG_MODULES logic

search_binary_handler() uses "for (try=0; try<2; try++)" to avoid "goto"
but the code looks too complicated and horrible imho.  We still need to
check "try == 0" before request_module() and add the additional "break"
for !CONFIG_MODULES case.

Kill this loop and use a simple "bool need_retry" + "goto retry".  The
code looks much simpler and we do not even need ifdef's, gcc can optimize
out the "if (need_retry)" block if !IS_ENABLED().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Zach Levis <zml@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/exec.c b/fs/exec.c
index 7b92fbf..ba357e6 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1367,13 +1367,15 @@ out:
 }
 EXPORT_SYMBOL(remove_arg_zero);
 
+#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
 /*
  * cycle the list of binary formats handler, until one recognizes the image
  */
 int search_binary_handler(struct linux_binprm *bprm)
 {
-       int try, retval;
+       bool need_retry = IS_ENABLED(CONFIG_MODULES);
        struct linux_binfmt *fmt;
+       int retval;
 
        /* This allows 4 levels of binfmt rewrites before failing hard. */
        if (bprm->recursion_depth > 5)
@@ -1388,47 +1390,39 @@ int search_binary_handler(struct linux_binprm *bprm)
                return retval;
 
        retval = -ENOENT;
-       for (try=0; try<2; try++) {
-               read_lock(&binfmt_lock);
-               list_for_each_entry(fmt, &formats, lh) {
-                       if (!try_module_get(fmt->module))
-                               continue;
-                       read_unlock(&binfmt_lock);
-                       bprm->recursion_depth++;
-                       retval = fmt->load_binary(bprm);
-                       bprm->recursion_depth--;
-                       if (retval >= 0) {
-                               put_binfmt(fmt);
-                               return retval;
-                       }
-                       read_lock(&binfmt_lock);
+ retry:
+       read_lock(&binfmt_lock);
+       list_for_each_entry(fmt, &formats, lh) {
+               if (!try_module_get(fmt->module))
+                       continue;
+               read_unlock(&binfmt_lock);
+               bprm->recursion_depth++;
+               retval = fmt->load_binary(bprm);
+               bprm->recursion_depth--;
+               if (retval >= 0) {
                        put_binfmt(fmt);
-                       if (retval != -ENOEXEC || bprm->mm == NULL)
-                               break;
-                       if (!bprm->file) {
-                               read_unlock(&binfmt_lock);
-                               return retval;
-                       }
+                       return retval;
                }
-               read_unlock(&binfmt_lock);
-#ifdef CONFIG_MODULES
-               if (retval != -ENOEXEC || bprm->mm == NULL) {
+               read_lock(&binfmt_lock);
+               put_binfmt(fmt);
+               if (retval != -ENOEXEC || bprm->mm == NULL)
                        break;
-               } else {
-#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
-                       if (printable(bprm->buf[0]) &&
-                           printable(bprm->buf[1]) &&
-                           printable(bprm->buf[2]) &&
-                           printable(bprm->buf[3]))
-                               break; /* -ENOEXEC */
-                       if (try)
-                               break; /* -ENOEXEC */
-                       request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
+               if (!bprm->file) {
+                       read_unlock(&binfmt_lock);
+                       return retval;
                }
-#else
-               break;
-#endif
        }
+       read_unlock(&binfmt_lock);
+
+       if (need_retry && retval == -ENOEXEC && bprm->mm) {
+               if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
+                   printable(bprm->buf[2]) && printable(bprm->buf[3]))
+                       return retval;
+               request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2));
+               need_retry = false;
+               goto retry;
+       }
+
        return retval;
 }
 EXPORT_SYMBOL(search_binary_handler);