Re: FAILED: patch "[PATCH] binder: use euid from cred instead of using task" failed to apply to 4.4-stable tree

Hi Greg. I'll post backports for these this week.

On Mon, Nov 8, 2021 at 11:23 PM gregkh@linuxfoundation.org wrote:

The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 29bc22ac5e5bc63275e850f0c8fc549e3d0e306b Mon Sep 17 00:00:00 2001 From: Todd Kjos tkjos@google.com Date: Tue, 12 Oct 2021 09:56:12 -0700 Subject: [PATCH] binder: use euid from cred instead of using task

Save the 'struct cred' associated with a binder process at initial open to avoid potential race conditions when converting to an euid.

Set a transaction's sender_euid from 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.

Cc: stable@vger.kernel.org # 4.4+ Fixes: 457b9a6f09f0 ("Staging: android: add binder driver") Signed-off-by: Todd Kjos tkjos@google.com Suggested-by: Stephen Smalley stephen.smalley.work@gmail.com Suggested-by: Jann Horn jannh@google.com Acked-by: Casey Schaufler casey@schaufler-ca.com Signed-off-by: Paul Moore paul@paul-moore.com

diff --git a/drivers/android/binder.c b/drivers/android/binder.c index d9030cb6b1e4..231cff9b3b75 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2702,7 +2702,7 @@ 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;
  

@@ -4343,6 +4343,7 @@ static void binder_free_proc(struct binder_proc *proc) } binder_alloc_deferred_release(&proc->alloc); put_task_struct(proc->tsk);

•   put_cred(proc->cred);
    binder_stats_deleted(BINDER_STAT_PROC);
    kfree(proc);
  

} @@ -5021,6 +5022,7 @@ static int binder_open(struct inode *nodp, struct file *filp) spin_lock_init(&proc->outer_lock); get_task_struct(current->group_leader); proc->tsk = current->group_leader;

•   proc->cred = get_cred(filp->f_cred);
    INIT_LIST_HEAD(&proc->todo);
    init_waitqueue_head(&proc->freeze_wait);
    proc->default_priority = task_nice(current);
  

diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h index 810c0b84d3f8..e7d4920b3368 100644 --- a/drivers/android/binder_internal.h +++ b/drivers/android/binder_internal.h @@ -364,6 +364,9 @@ struct binder_ref {

•                    (invariant after initialized)
  

• @tsk task_struct for group_leader of process

•                    (invariant after initialized)
  

• • @cred struct cred associated with the `struct file`

• •                    in binder_open()
    

• •                    (invariant after initialized)
    

  • @deferred_work_node: element for binder_deferred_list

  •                    (protected by binder_deferred_lock)
    

  • @deferred_work: bitmap of deferred work to perform

@@ -424,6 +427,7 @@ struct binder_proc { struct list_head waiting_threads; int pid; struct task_struct *tsk;

•   const struct cred *cred;
    struct hlist_node deferred_work_node;
    int deferred_work;
    int outstanding_txns;