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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>
This commit is contained in:
Oleg Nesterov 2013-09-11 14:24:44 -07:00 committed by Linus Torvalds
parent 92eaa565ad
commit cb7b6b1cbc
1 changed files with 33 additions and 39 deletions
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72
fs/exec.c
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@ -1367,13 +1367,15 @@ int remove_arg_zero(struct linux_binprm *bprm)
}
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);
put_binfmt(fmt);
if (retval != -ENOEXEC || bprm->mm == NULL)
break;
if (!bprm->file) {
read_unlock(&binfmt_lock);
return retval;
}
}
retry:
read_lock(&binfmt_lock);
list_for_each_entry(fmt, &formats, lh) {
if (!try_module_get(fmt->module))
continue;
read_unlock(&binfmt_lock);
#ifdef CONFIG_MODULES
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]));
bprm->recursion_depth++;
retval = fmt->load_binary(bprm);
bprm->recursion_depth--;
if (retval >= 0) {
put_binfmt(fmt);
return retval;
}
read_lock(&binfmt_lock);
put_binfmt(fmt);
if (retval != -ENOEXEC || bprm->mm == NULL)
break;
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);