[ 18/85] vfs: canonicalize create mode in build_open_flags()

[Greg Kroah-Hartman]

From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>

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

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

From: Miklos Szeredi <mszeredi@xxxxxxx>

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@xxxxxxx>
Tested-by: Richard W.M. Jones <rjones@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/open.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/fs/open.c
+++ b/fs/open.c
@@ -882,9 +882,10 @@ static inline int build_open_flags(int f
 	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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