linux-kernel - [PATCH 2/3] exec: kill "int depth" in search_binary

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Message-ID: <20130801190514.GA3216@redhat.com>
Date:	Thu, 1 Aug 2013 21:05:14 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Zach Levis <zml@...ux.vnet.ibm.com>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Evgeniy Polyakov <zbr@...emap.net>,
	Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] exec: kill "int depth" in search_binary_handler()

Nobody except search_binary_handler() should touch ->recursion_depth,
"int depth" buys nothing but complicates the code, kill it.

Probably we should also kill "fn" and the !NULL check, ->load_binary
should be always defined. And it can not go away after read_unlock()
or this code is buggy anyway.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 fs/exec.c |    9 ++++-----
 1 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index a9ae4f2..f32079c 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1370,12 +1370,11 @@ EXPORT_SYMBOL(remove_arg_zero);
  */
 int search_binary_handler(struct linux_binprm *bprm)
 {
-	unsigned int depth = bprm->recursion_depth;
-	int try,retval;
+	int try, retval;
 	struct linux_binfmt *fmt;
 
 	/* This allows 4 levels of binfmt rewrites before failing hard. */
-	if (depth > 5)
+	if (bprm->recursion_depth > 5)
 		return -ELOOP;
 
 	retval = security_bprm_check(bprm);
@@ -1396,9 +1395,9 @@ int search_binary_handler(struct linux_binprm *bprm)
 			if (!try_module_get(fmt->module))
 				continue;
 			read_unlock(&binfmt_lock);
-			bprm->recursion_depth = depth + 1;
+			bprm->recursion_depth++;
 			retval = fn(bprm);
-			bprm->recursion_depth = depth;
+			bprm->recursion_depth--;
 			if (retval >= 0) {
 				put_binfmt(fmt);
 				allow_write_access(bprm->file);
-- 
1.5.5.1

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