linux-kernel - Re: [PATCH v3 3/3] binder: use euid from cred instead of using task

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Date:   Wed, 6 Oct 2021 12:55:13 -0700
From:   Todd Kjos <tkjos@...gle.com>
To:     gregkh@...uxfoundation.org, arve@...roid.com, tkjos@...roid.com,
        maco@...roid.com, christian@...uner.io, jmorris@...ei.org,
        serge@...lyn.com, paul@...l-moore.com,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        keescook@...omium.org, jannh@...gle.com, jeffv@...gle.com,
        zohar@...ux.ibm.com, linux-security-module@...r.kernel.org,
        selinux@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Cc:     joel@...lfernandes.org, kernel-team@...roid.com,
        stable@...r.kernel.org
Subject: Re: [PATCH v3 3/3] binder: use euid from cred instead of using task

On Wed, Oct 6, 2021 at 12:46 PM Todd Kjos <tkjos@...gle.com> wrote:
>
> Set a transaction's sender_euid from the the 'struct cred'
> saved at binder_open() instead of looking up the euid
> from the binder proc's 'struct task'. This ensures
> the euid is associated with the security context that
> of the task that opened binder.
>
> Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
> Signed-off-by: Todd Kjos <tkjos@...gle.com>
> Stephen Smalley <stephen.smalley.work@...il.com>

This should have been "Suggested-by: Stephen Smalley
<stephen.smalley.work@...il.com>"

> Cc: stable@...r.kernel.org # 4.4+
> ---
> v3: added this patch to series
>
>  drivers/android/binder.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 989afd0804ca..26382e982c5e 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -2711,7 +2711,7 @@ static void binder_transaction(struct binder_proc *proc,
>                 t->from = thread;
>         else
>                 t->from = NULL;
> -       t->sender_euid = task_euid(proc->tsk);
> +       t->sender_euid = proc->cred->euid;
>         t->to_proc = target_proc;
>         t->to_thread = target_thread;
>         t->code = tr->code;
> --
> 2.33.0.800.g4c38ced690-goog
>