binder: fix OOB in binder_add_freeze_work()

In binder_add_freeze_work() we iterate over the proc->nodes with the
proc->inner_lock held. However, this lock is temporarily dropped to
acquire the node->lock first (lock nesting order). This can race with
binder_deferred_release() which removes the nodes from the proc->nodes
rbtree and adds them into binder_dead_nodes list. This leads to a broken
iteration in binder_add_freeze_work() as rb_next() will use data from
binder_dead_nodes, triggering an out-of-bounds access:

  ==================================================================
  BUG: KASAN: global-out-of-bounds in rb_next+0xfc/0x124
  Read of size 8 at addr ffffcb84285f7170 by task freeze/660

  CPU: 8 UID: 0 PID: 660 Comm: freeze Not tainted 6.11.0-07343-ga727812a8d45 #18
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   rb_next+0xfc/0x124
   binder_add_freeze_work+0x344/0x534
   binder_ioctl+0x1e70/0x25ac
   __arm64_sys_ioctl+0x124/0x190

  The buggy address belongs to the variable:
   binder_dead_nodes+0x10/0x40
  [...]
  ==================================================================

This is possible because proc->nodes (rbtree) and binder_dead_nodes
(list) share entries in binder_node through a union:

	struct binder_node {
	[...]
		union {
			struct rb_node rb_node;
			struct hlist_node dead_node;
		};

Fix the race by checking that the proc is still alive. If not, simply
break out of the iteration.

Fixes: d579b04a52a1 ("binder: frozen notification")
Cc: stable@vger.kernel.org
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20240926233632.821189-3-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 4d90203ea048803b8fbd1b7dfa119bae692959c1..8bca2de6fa242b346960dff0864e0eeee1bcdfce 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -5593,6 +5593,8 @@ static void binder_add_freeze_work(struct binder_proc *proc, bool is_frozen)
                prev = node;
                binder_node_unlock(node);
                binder_inner_proc_lock(proc);
+               if (proc->is_dead)
+                       break;
        }
        binder_inner_proc_unlock(proc);
        if (prev)