linux-kernel - [PATCH 2/3] Check node type at the beginning of mknodat

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Message-Id: <1340940558-9893-2-git-send-email-yan@linux.vnet.ibm.com>
Date:	Fri, 29 Jun 2012 11:29:17 +0800
From:	Guo Chao <yan@...ux.vnet.ibm.com>
To:	viro@...iv.linux.org.uk
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] Check node type at the beginning of mknodat

We make sure node is not directory at beginning of mknodat, which is in 
effect included in a latter may_mknod check.

Move may_mknod up to replace directory check. We can also avoid cleanup 
if check fails.

Signed-off-by: Guo Chao <yan@...ux.vnet.ibm.com>
---
 fs/namei.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 8dccfcc..05b9053 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2910,8 +2910,9 @@ SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
 	struct path path;
 	int error;
 
-	if (S_ISDIR(mode))
-		return -EPERM;
+	error = may_mknod(mode);
+	if (error)
+		return error;
 
 	dentry = user_path_create(dfd, filename, &path, 0);
 	if (IS_ERR(dentry))
@@ -2919,9 +2920,7 @@ SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
 
 	if (!IS_POSIXACL(path.dentry->d_inode))
 		mode &= ~current_umask();
-	error = may_mknod(mode);
-	if (error)
-		goto out_dput;
+
 	error = mnt_want_write(path.mnt);
 	if (error)
 		goto out_dput;
-- 
1.7.9.5

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