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FAILED: patch "[PATCH] binder: use euid from cred instead of using task" failed to apply to 4.19-stable tree

PATCH [email protected] 1 participant 1 message Nov 9, 2021

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The patch below does not apply to the 4.19-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;