As tracer is NULL in the exist case, ca_get_task_policy() has
not been called, so a direct exit looks ok.

John Johansen wrote:
> BugLink: http://bugs.launchpad.net/bugs/480112
>
> SRU Justification: This bug can cause confined process to oops at address 0.
> This can occur when executing a process if the LSM_UNSAFE_PTRACE |
> LSM_UNSAFE_PTRACE_CAP flags are set. The likely hood of if/how often this
> will occur depends on if ptrace is being used.
>
> As reported by Tetsuo Handa on kernel-team mailing list:
>
> In aa_may_change_ptraced_domain, if (!tracer) cred == NULL, and
> put_cred(cred) will oops. This will only happen on exec if the task
> is marked as LSM_UNSAFE_PTRACE | LSM_UNSAFE_PTRACE_CAP, so should
> only happen to ptraced tasks that are confined.
>
> Fix this by returning directly from aa_may_change_ptrace_domain if
> there is now tracer.
>
> Signed-off-by: John Johansen <john.johansen@canonical.com>

Acked-by: Stefan Bader <stefan.bader@canonical.com>

> ---
> ubuntu/apparmor/domain.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/ubuntu/apparmor/domain.c b/ubuntu/apparmor/domain.c
> index fe89ddc..12e45c6 100644
> --- a/ubuntu/apparmor/domain.c
> +++ b/ubuntu/apparmor/domain.c
> @@ -64,6 +64,10 @@ static int aa_may_change_ptraced_domain(struct task_struct *task,
> cred = aa_get_task_policy(tracer, &tracerp);
> rcu_read_unlock();
>
> + /* not ptraced */
> + if (!tracer)
> + return 0;
> +
> if (!tracerp)
> goto out;
>


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