linux-kernel - [PATCH 3/4] binder: fix freeze UAF in binder_release

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Message-ID: <20240924184401.76043-4-cmllamas@google.com>
Date: Tue, 24 Sep 2024 18:43:55 +0000
From: Carlos Llamas <cmllamas@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Arve Hjønnevåg" <arve@...roid.com>, Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>, 
	Joel Fernandes <joel@...lfernandes.org>, Christian Brauner <brauner@...nel.org>, 
	Carlos Llamas <cmllamas@...gle.com>, Suren Baghdasaryan <surenb@...gle.com>, 
	Yu-Ting Tseng <yutingtseng@...gle.com>
Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com, 
	Alice Ryhl <aliceryhl@...gle.com>, stable@...r.kernel.org
Subject: [PATCH 3/4] binder: fix freeze UAF in binder_release_work()

When a binder reference is cleaned up, any freeze work queued in the
associated process should also be removed. Otherwise, the reference is
freed while its ref->freeze.work is still queued in proc->work leading
to a use-after-free issue as shown by the following KASAN report:

  ==================================================================
  BUG: KASAN: slab-use-after-free in binder_release_work+0x398/0x3d0
  Read of size 8 at addr ffff31600ee91488 by task kworker/5:1/211

  CPU: 5 UID: 0 PID: 211 Comm: kworker/5:1 Not tainted 6.11.0-rc7-00382-gfc6c92196396 #22
  Hardware name: linux,dummy-virt (DT)
  Workqueue: events binder_deferred_func
  Call trace:
   binder_release_work+0x398/0x3d0
   binder_deferred_func+0xb60/0x109c
   process_one_work+0x51c/0xbd4
   worker_thread+0x608/0xee8

  Allocated by task 703:
   __kmalloc_cache_noprof+0x130/0x280
   binder_thread_write+0xdb4/0x42a0
   binder_ioctl+0x18f0/0x25ac
   __arm64_sys_ioctl+0x124/0x190
   invoke_syscall+0x6c/0x254

  Freed by task 211:
   kfree+0xc4/0x230
   binder_deferred_func+0xae8/0x109c
   process_one_work+0x51c/0xbd4
   worker_thread+0x608/0xee8
  ==================================================================

This commit fixes the issue by ensuring any queued freeze work is removed
when cleaning up a binder reference.

Fixes: d579b04a52a1 ("binder: frozen notification")
Cc: stable@...r.kernel.org
Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
---
 drivers/android/binder.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 8bca2de6fa24..d955135ee37a 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -1225,6 +1225,12 @@ static void binder_cleanup_ref_olocked(struct binder_ref *ref)
 		binder_dequeue_work(ref->proc, &ref->death->work);
 		binder_stats_deleted(BINDER_STAT_DEATH);
 	}
+
+	if (ref->freeze) {
+		binder_dequeue_work(ref->proc, &ref->freeze->work);
+		binder_stats_deleted(BINDER_STAT_FREEZE);
+	}
+
 	binder_stats_deleted(BINDER_STAT_REF);
 }
 
-- 
2.46.0.792.g87dc391469-goog