linux-kernel - [PATCH 1/4] vfs: canonicalize create mode in build_open

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Date:	Tue,  7 Aug 2012 14:45:46 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	viro@...IV.linux.org.uk
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	rjones@...hat.com, steveamigauk@...oo.co.uk, mszeredi@...e.cz,
	stable@...r.kernel.org
Subject: [PATCH 1/4] vfs: canonicalize create mode in build_open_flags()

From: Miklos Szeredi <mszeredi@...e.cz>

Userspace can pass weird create mode in open(2) that we canonicalize to
"(mode & S_IALLUGO) | S_IFREG" in vfs_create().

The problem is that we use the uncanonicalized mode before calling vfs_create()
with unforseen consequences.

So do the canonicalization early in build_open_flags().

Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
CC: stable@...r.kernel.org
---
 fs/open.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index bc132e1..e1f2cdb 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -852,9 +852,10 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
 	int lookup_flags = 0;
 	int acc_mode;
 
-	if (!(flags & O_CREAT))
-		mode = 0;
-	op->mode = mode;
+	if (flags & O_CREAT)
+		op->mode = (mode & S_IALLUGO) | S_IFREG;
+	else
+		op->mode = 0;
 
 	/* Must never be set by userspace */
 	flags &= ~FMODE_NONOTIFY;
-- 
1.7.7

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