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

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 <[email protected]>.

thanks,

greg k-h

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

From 29bc22ac5e5bc63275e850f0c8fc549e3d0e306b Mon Sep 17 00:00:00 2001
From: Todd Kjos <[email protected]>
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 [email protected] # 4.4+

Fixes 457b9a6f09f0 ("Staging: android: add binder driver")

Signed-off-by Todd Kjos <[email protected]>

Suggested-by Stephen Smalley <[email protected]>

Suggested-by Jann Horn <[email protected]>

Acked-by Casey Schaufler <[email protected]>

Signed-off-by Paul Moore <[email protected]>

drivers/android/binder.c +3 -1

index d9030cb6b1e4..231cff9b3b75 100644
@@ -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);

drivers/android/binder_internal.h +4 -0

index 810c0b84d3f8..e7d4920b3368 100644
@@ -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;

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

Quoted 33 lines

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 <[email protected]>.

thanks,

greg k-h

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

From 29bc22ac5e5bc63275e850f0c8fc549e3d0e306b Mon Sep 17 00:00:00 2001
From: Todd Kjos <[email protected]>
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 [email protected] # 4.4+

Fixes 457b9a6f09f0 ("Staging: android: add binder driver")

Signed-off-by Todd Kjos <[email protected]>

Suggested-by Stephen Smalley <[email protected]>

Suggested-by Jann Horn <[email protected]>

Acked-by Casey Schaufler <[email protected]>

Signed-off-by Paul Moore <[email protected]>