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Old 11-12-2009, 10:25 AM
Andy Whitcroft
 
Default UBUNTU: SAUCE: AppArmor: Fix refcounting bug causing leak of creds

On Tue, Nov 10, 2009 at 10:29:12AM -0800, John Johansen wrote:
> BugLink: http://bugs.launchpad.net/bugs/479115
>
> SRU Justification: Failure to put the cred causes a memory leak that is
> larger than the cred struct, as it leaks everything it references. This
> happens for every unconfined processes that does an exec, change_hat or
> change_profile and passes through this function.
>
> AppArmor when doing ptrace check for domain changes, fails to drop
> the ref count on the task creds when it is unconfined.
>
> Signed-off-by: John Johansen <john.johansen@canonical.com>
> ---
> ubuntu/apparmor/domain.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/ubuntu/apparmor/domain.c b/ubuntu/apparmor/domain.c
> index 128e527..fe89ddc 100644
> --- a/ubuntu/apparmor/domain.c
> +++ b/ubuntu/apparmor/domain.c
> @@ -65,9 +65,10 @@ static int aa_may_change_ptraced_domain(struct task_struct *task,
> rcu_read_unlock();
>
> if (!tracerp)
> - return error;
> + goto out;
>
> error = aa_may_ptrace(tracer, tracerp, to_profile, PTRACE_MODE_ATTACH);
> +out:
> put_cred(cred);
>
> return error;

Ok, the change itself looks fine if we have taken the cred reference we
should return it.

I just want to confirm that aa_get_task_policy() cannot return a valid
tracerp but a null cred? Else the put_cred() might oops. A quick look
at that seems to say its ok. Assuming that is true:

Acked-by: Andy Whitcroft <apw@canonical.com>

-apw

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