Re: [PATCH 4/5] selinux: Enhance selinux to always ignore private inodes.

Stephen Smalley
2007-02-09T12:30:54Z

On Thu, 2007-02-08 at 16:02 -0700, Eric W. Biederman wrote:
> From: Stephen Smalley <sds@tycho.nsa.gov>
>
> Hmmm...turns out to not be quite enough, as the /proc/sys inodes aren't
> truly private to the fs, so we can run into them in a variety of
> security hooks beyond just the inode hooks, such as
> security_file_permission (when reading and writing them via the vfs
> helpers), security_sb_mount (when mounting other filesystems on
> directories in proc like binfmt_misc), and deeper within the security
> module itself (as in flush_unauthorized_files upon inheritance across
> execve). So I think we have to add an IS_PRIVATE() guard within
> SELinux, as below. Note however that the use of the private flag here
> could be confusing, as these inodes are _not_ private to the fs, are
> exposed to userspace, and security modules must implement the sysctl
> hook to get any access control over them.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>

> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
>
> ---
> security/selinux/hooks.c | 3 +++
> 1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index de16b9f..ff9fccc 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -1077,6 +1077,9 @@ static int inode_has_perm(struct task_struct *tsk,
> struct inode_security_struct *isec;
> struct avc_audit_data ad;
>
> + if (unlikely (IS_PRIVATE (inode)))
> + return 0;
> +
> tsec = tsk->security;
> isec = inode->i_security;
>
--
Stephen Smalley
National Security Agency