From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f194.google.com ([209.85.128.194]:32948 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756087AbdDGJBn (ORCPT ); Fri, 7 Apr 2017 05:01:43 -0400 From: Amir Goldstein To: Miklos Szeredi Cc: Al Viro , linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v2 3/3] ovl: check IS_APPEND() on real upper inode Date: Fri, 7 Apr 2017 12:01:41 +0300 Message-Id: <1491555701-16608-4-git-send-email-amir73il@gmail.com> In-Reply-To: <1491555701-16608-1-git-send-email-amir73il@gmail.com> References: <1491555701-16608-1-git-send-email-amir73il@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: For overlay file open, check IS_APPEND() on the real upper inode inside d_real(), because the overlay inode does not have the S_APPEND flag and IS_APPEND() can only be checked at open time. Note that because overlayfs does not copy up the chattr inode flags (i.e. S_APPEND, S_IMMUTABLE), the IS_APPEND() check is only relevant for upper inodes that were set with chattr +a and not to lower inodes that had chattr +a before copy up. Signed-off-by: Amir Goldstein --- fs/overlayfs/super.c | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index c9e70d3..13806b8 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -49,11 +49,30 @@ static void ovl_dentry_release(struct dentry *dentry) } } +static int ovl_may_open(struct dentry *dentry, int flag) +{ + struct inode *inode = dentry->d_inode; + + /* + * This test was moot in vfs may_open() because overlay inode does + * not have the S_APPEND flag + */ + if (IS_APPEND(inode)) { + if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) + return -EPERM; + if (flag & O_TRUNC) + return -EPERM; + } + + return 0; +} + static struct dentry *ovl_d_real(struct dentry *dentry, const struct inode *inode, unsigned int open_flags) { struct dentry *real; + int err; if (!d_is_reg(dentry)) { if (!inode || inode == d_inode(dentry)) @@ -65,15 +84,20 @@ static struct dentry *ovl_d_real(struct dentry *dentry, return dentry; if (open_flags) { - int err = ovl_open_maybe_copy_up(dentry, open_flags); - + err = ovl_open_maybe_copy_up(dentry, open_flags); if (err) return ERR_PTR(err); } real = ovl_dentry_upper(dentry); - if (real && (!inode || inode == d_inode(real))) + if (real && (!inode || inode == d_inode(real))) { + if (!inode) { + err = ovl_may_open(real, open_flags); + if (err) + return ERR_PTR(err); + } return real; + } real = ovl_dentry_lower(dentry); if (!real) -- 2.7.4