From mboxrd@z Thu Jan 1 00:00:00 1970 From: Casey Schaufler Subject: Re: [PATCH 12/13] ovl: switch to __inode_permission() Date: Wed, 15 Aug 2012 09:59:51 -0700 Message-ID: <502BD587.6090807@schaufler-ca.com> References: <1345045700-9062-1-git-send-email-miklos@szeredi.hu> <1345045700-9062-13-git-send-email-miklos@szeredi.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: viro@ZenIV.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, apw@canonical.com, nbd@openwrt.org, neilb@suse.de, hramrach@centrum.cz, jordipujolp@gmail.com, ezk@fsl.cs.sunysb.edu, ricwheeler@gmail.com, dhowells@redhat.com, hpj@urpla.net, sedat.dilek@googlemail.com, penberg@kernel.org, goran.cetusic@gmail.com, romain@orebokech.com, mszeredi@suse.cz, Casey Schaufler To: Miklos Szeredi Return-path: In-Reply-To: <1345045700-9062-13-git-send-email-miklos@szeredi.hu> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 8/15/2012 8:48 AM, Miklos Szeredi wrote: > From: Andy Whitcroft > > When checking permissions on an overlayfs inode we do not take into > account either device cgroup restrictions nor security permissions. > This allows a user to mount an overlayfs layer over a restricted device > directory and by pass those permissions to open otherwise restricted > files. Why is this a good idea? Either you're not including enough context about the conditions under which this can occur, or you're suggesting the introduction of a trivial mechanism for bypassing all file access controls. This does not seem right. > > Switch over to __inode_permissions. > > Signed-off-by: Andy Whitcroft > Signed-off-by: Miklos Szeredi > --- > fs/overlayfs/inode.c | 12 +----------- > 1 files changed, 1 insertions(+), 11 deletions(-) > > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c > index e854720..f3a534f 100644 > --- a/fs/overlayfs/inode.c > +++ b/fs/overlayfs/inode.c > @@ -100,19 +100,9 @@ int ovl_permission(struct inode *inode, int mask) > if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && > (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) > goto out_dput; > - > - /* > - * Nobody gets write access to an immutable file. > - */ > - err = -EACCES; > - if (IS_IMMUTABLE(realinode)) > - goto out_dput; > } > > - if (realinode->i_op->permission) > - err = realinode->i_op->permission(realinode, mask); > - else > - err = generic_permission(realinode, mask); > + err = __inode_permission(realinode, mask); > out_dput: > dput(alias); > return err;