Re: [RFC PATCH 0/9][V3] Overlayfs SELinux Support
From: Paul Moore
Date: Thu Jul 21 2016 - 17:16:48 EST
On Wed, Jul 13, 2016 at 10:44 AM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
> Hi All,
> Please find attached the V3 of patches. Changes since V2 are as follows.
> - Fixed the build issue with CONFIG_SECURITY=n.
> - Dan Walsh was writing more tests for selinux-testsuite and noted couple
> of issues. I have fixed those issues and added two more patches in series.
> 1. We are resetting MAY_WRITE check for lower inode assuming file will
> be coiped up. But this is not true for special_file() as these files
> are not copied up. So checks should not be reset in case of special
> 2. We are resetting MAY_WRITE check for lower inode assuming file will
> be copied up. But this also should mean that mounter has permission
> to MAY_READ lower file for copy up to succeed. So add MAY_READ
> check while resetting MAY_WRITE.
> Original description of patches follows.
> Following are RFC patches to support SELinux with overlayfs. I started
> with David Howells's latest posting on this topic and started modifying
> patches. These patches apply on top of overlayfs-next branch of miklos
> vfs git tree.
> git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs-next
> These patches can be pulled from my branch too.
> Thanks to Dan Walsh, Stephen Smalley and Miklos Szeredi for numerous
> conversation and ideas in helping figuring out what one reasonable
> implementation might look like.
> Dan Walsh has been writing tests for selinux overlayfs in selinux-testsuite.
> These patches pass those tests now
> Posting these patches for review and comments.
> These patches introduce 3 new security hooks.
> - security_inode_copy_up(), is called when a file is copied up. This hook
> prepares a new set of cred which is used for copy up operation. And
> new set of creds are prepared so that ->create_sid can be set appropriately
> and newly created file is labeled properly.
> When a file is copied up, label of lower file is retained except for the
> case of context= mount where new file gets the label from context= option.
> - security_inode_copy_up_xattr(), is called when xattrs of a file are
> being copied up. Before this we already called security_inode_copy_up()
> and created new file and copied up data. That means file already got
> labeled properly and there is no need to take SELINUX xattr of lower
> file and overwrite the upper file xattr. So this hook is used to avoid
> copying up of SELINUX xattr.
> - dentry_create_files_as(), is called when a new file is about to be created.
> This hook determines what the label of the file should be if task had
> created that file in upper/ and sets create_sid accordingly in the passed
> in creds.
> Normal transition rules don't work for the case of context mounts as
> underlying file system is not aware of context option which only overlay
> layer is aware of. For non-context mounts, creation can happen in work/
> dir first and then file might be renamed into upper/, and it might get
> label based on work/ dir. So this hooks helps avoiding all these issues.
> When a new file is created in upper/, it gets its label based on transition
> rules. For the case of context mount, it gets the label from context=
> Any feedback is welcome.
These patches look fine to me, thanks for all your hard work and to
everyone who helped review and provide feedback. I have tagged these
patches for merging into the SELinux next branch after this merge
Miklos, this patchset depends on patches in your overlayfs-next
branch, I assume you're pushing that branch during the upcoming merge
James, assuming the overlayfs-next branch is pulled during the merge
window, can you rebase your linux-security#next branch to v4.8-rc1
once Linus tags it?