[PATCH 3/5] exec: cleanup the CONFIG_MODULES logic

Oleg Nesterov
2013-08-02T19:33:53Z

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>
---
fs/exec.c | 68 +++++++++++++++++++++++++++---------------------------------
1 files changed, 31 insertions(+), 37 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 9f41e7d..48344a2 100644
--- 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);
--
1.5.5.1