vfs: canonicalize create mode in build_open_flags()

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@suse.cz>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/open.c b/fs/open.c
index e2b5d51..b8485d3 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -882,9 +882,10 @@ static inline int build_open_flags(int flags, int mode, struct open_flags *op)
        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;