linux-kernel - [PATCH] module: report -EFAULT on bytes remaining

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Date:	Wed, 12 Sep 2012 08:06:16 -0700
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Fengguang Wu <fengguang.wu@...el.com>,
	kernel-janitors@...r.kernel.org,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Dan Carpenter <dan.carpenter@...cle.com>
Subject: [PATCH] module: report -EFAULT on bytes remaining

Caught by smatch:
kernel/module.c:2450 copy_module_from_user() warn: maybe return -EFAULT instead of the bytes remaining?  

Clean up the copy_from_user() call to not report a positive value.
With this patch, init_module() will report errors from copy_from_user
(before it would always only report -EFAULT when err != 0).

Reported-by: Fengguang Wu <fengguang.wu@...el.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
This change is on top of the finit_module patch series.
---
 kernel/module.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 0ad03c4..05b8dde 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2441,8 +2441,11 @@ int copy_module_from_user(const void __user *umod, unsigned long len,
 		return -ENOMEM;
 
 	err = copy_from_user(info->hdr, umod, info->len);
-	if (err)
+	if (err) {
+		if (err > 0)
+			err = -EFAULT;
 		goto free_hdr;
+	}
 
 	err = check_info(info);
 	if (err)
-- 
1.7.0.4


-- 
Kees Cook
Chrome OS Security
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