linux-kernel - [PATCH v2 8/8] exec: cleanup the error handling in search_binary

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Message-ID: <20130805134148.GA15656@redhat.com>
Date:	Mon, 5 Aug 2013 15:41:48 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Evgeniy Polyakov <zbr@...emap.net>,
	Kees Cook <keescook@...omium.org>,
	Zach Levis <zml@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 8/8] exec: cleanup the error handling in
	search_binary_handler()

The error hanling and ret-from-loop look confusing and inconsistent.

- "retval >= 0" simply returns

- "!bprm->file" returns too but with read_unlock() because
   binfmt_lock was already re-acquired

- "retval != -ENOEXEC || bprm->mm == NULL" does "break" and
  relies on the same check after the main loop

Consolidate these checks into a single if/return statement.

need_retry still checks "retval == -ENOEXEC", but this and -ENOENT
before the main loop are not needed. This is only for pathological
and impossible list_empty(&formats) case.

It is not clear why do we check "bprm->mm == NULL", probably this
should be removed.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Kees Cook <keescook@...omium.org>
---
 fs/exec.c |   11 +++--------
 1 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 682895d..eb2f05a 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1399,22 +1399,17 @@ int search_binary_handler(struct linux_binprm *bprm)
 		bprm->recursion_depth++;
 		retval = fmt->load_binary(bprm);
 		bprm->recursion_depth--;
-		if (retval >= 0) {
+		if (retval >= 0 || retval != -ENOEXEC ||
+		    bprm->mm == NULL || bprm->file == NULL) {
 			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;
-		}
 	}
 	read_unlock(&binfmt_lock);
 
-	if (need_retry && retval == -ENOEXEC && bprm->mm) {
+	if (need_retry && retval == -ENOEXEC) {
 		if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
 		    printable(bprm->buf[2]) && printable(bprm->buf[3]))
 			return retval;
-- 
1.5.5.1

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