linux-kernel - [ 31/95] vfs: canonicalize create mode in build_open

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Date:	Sun, 09 Sep 2012 23:42:21 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Miklos Szeredi <mszeredi@...e.cz>,
	"Richard W.M. Jones" <rjones@...hat.com>
Subject: [ 31/95] vfs: canonicalize create mode in build_open_flags()

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit e68726ff72cf7ba5e7d789857fcd9a75ca573f03 upstream.

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>
Tested-by: Richard W.M. Jones <rjones@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/open.c |    7 ++++---
 1 file 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;


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