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Date: Mon, 13 Aug 2012 14:45:30 +0300
From: Jarkko Sakkinen <jarkko.sakkinen@...el.com>
To: Casey Schaufler <casey@...aufler-ca.com>
Cc: linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH] Smack: remove task_wait() hook.
On Thu, Aug 09, 2012 at 05:46:38PM -0700, Casey Schaufler wrote:
> On 12/20/2011 11:20 PM, Jarkko Sakkinen wrote:
> > Allow SIGCHLD to be passed to child process without
> > explicit policy. This will help to keep the access
> > control policy simple and easily maintainable with
> > complex applications that require use of multiple
> > security contexts. It will also help to keep them
> > as isolated as possible.
> >
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...el.com>
>
> I have a slightly different version that applies to the
> current smack-next tree.
>
> Allow SIGCHLD to be passed to child process without
> explicit policy. This will help to keep the access
> control policy simple and easily maintainable with
> complex applications that require use of multiple
> security contexts. It will also help to keep them
> as isolated as possible.
>
> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
Acked-by: Jarkko Sakkinen <jarkko.sakkinen@...el.com>
>
> security/smack/smack_lsm.c | 37 ++++++++-----------------------------
> 1 files changed, 8 insertions(+), 29 deletions(-)
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 8221514..ce9273a 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -1691,40 +1691,19 @@ static int smack_task_kill(struct task_struct *p, struct siginfo *info,
> * smack_task_wait - Smack access check for waiting
> * @p: task to wait for
> *
> - * Returns 0 if current can wait for p, error code otherwise
> + * Returns 0
> */
> static int smack_task_wait(struct task_struct *p)
> {
> - struct smk_audit_info ad;
> - char *sp = smk_of_current();
> - char *tsp = smk_of_forked(task_security(p));
> - int rc;
> -
> - /* we don't log here, we can be overriden */
> - rc = smk_access(tsp, sp, MAY_WRITE, NULL);
> - if (rc == 0)
> - goto out_log;
> -
> /*
> - * Allow the operation to succeed if either task
> - * has privilege to perform operations that might
> - * account for the smack labels having gotten to
> - * be different in the first place.
> - *
> - * This breaks the strict subject/object access
> - * control ideal, taking the object's privilege
> - * state into account in the decision as well as
> - * the smack value.
> + * Allow the operation to succeed.
> + * Zombies are bad.
> + * In userless environments (e.g. phones) programs
> + * get marked with SMACK64EXEC and even if the parent
> + * and child shouldn't be talking the parent still
> + * may expect to know when the child exits.
> */
> - if (smack_privileged(CAP_MAC_OVERRIDE) ||
> - has_capability(p, CAP_MAC_OVERRIDE))
> - rc = 0;
> - /* we log only if we didn't get overriden */
> - out_log:
> - smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
> - smk_ad_setfield_u_tsk(&ad, p);
> - smack_log(tsp, sp, MAY_WRITE, rc, &ad);
> - return rc;
> + return 0;
> }
>
> /**
>
> > ---
> > security/smack/smack_lsm.c | 40 ----------------------------------------
> > 1 files changed, 0 insertions(+), 40 deletions(-)
> >
> > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> > index 7db62b4..cc788f5 100644
> > --- a/security/smack/smack_lsm.c
> > +++ b/security/smack/smack_lsm.c
> > @@ -1685,45 +1685,6 @@ static int smack_task_kill(struct task_struct *p, struct siginfo *info,
> > }
> >
> > /**
> > - * smack_task_wait - Smack access check for waiting
> > - * @p: task to wait for
> > - *
> > - * Returns 0 if current can wait for p, error code otherwise
> > - */
> > -static int smack_task_wait(struct task_struct *p)
> > -{
> > - struct smk_audit_info ad;
> > - char *sp = smk_of_current();
> > - char *tsp = smk_of_forked(task_security(p));
> > - int rc;
> > -
> > - /* we don't log here, we can be overriden */
> > - rc = smk_access(tsp, sp, MAY_WRITE, NULL);
> > - if (rc == 0)
> > - goto out_log;
> > -
> > - /*
> > - * Allow the operation to succeed if either task
> > - * has privilege to perform operations that might
> > - * account for the smack labels having gotten to
> > - * be different in the first place.
> > - *
> > - * This breaks the strict subject/object access
> > - * control ideal, taking the object's privilege
> > - * state into account in the decision as well as
> > - * the smack value.
> > - */
> > - if (capable(CAP_MAC_OVERRIDE) || has_capability(p, CAP_MAC_OVERRIDE))
> > - rc = 0;
> > - /* we log only if we didn't get overriden */
> > - out_log:
> > - smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
> > - smk_ad_setfield_u_tsk(&ad, p);
> > - smack_log(tsp, sp, MAY_WRITE, rc, &ad);
> > - return rc;
> > -}
> > -
> > -/**
> > * smack_task_to_inode - copy task smack into the inode blob
> > * @p: task to copy from
> > * @inode: inode to copy to
> > @@ -3549,7 +3510,6 @@ struct security_operations smack_ops = {
> > .task_getscheduler = smack_task_getscheduler,
> > .task_movememory = smack_task_movememory,
> > .task_kill = smack_task_kill,
> > - .task_wait = smack_task_wait,
> > .task_to_inode = smack_task_to_inode,
> >
> > .ipc_permission = smack_ipc_permission,
>
/Jarkko
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