linux-kernel - [PATCH] binderfs: fix use-after-free in binder

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Message-ID: <20250130215823.1518990-1-cmllamas@google.com>
Date: Thu, 30 Jan 2025 21:58:22 +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>, Li Li <dualli@...gle.com>
Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com, 
	syzbot+7015dcf45953112c8b45@...kaller.appspotmail.com
Subject: [PATCH] binderfs: fix use-after-free in binder_devices

Devices created through binderfs are added to the global binder_devices
list but are not removed before being destroyed. This leads to dangling
pointers in the list and subsequent use-after-free errors:

  ==================================================================
  BUG: KASAN: slab-use-after-free in binder_add_device+0x5c/0x9c
  Write of size 8 at addr ffff0000c258d708 by task mount/653

  CPU: 7 UID: 0 PID: 653 Comm: mount Not tainted 6.13.0-09030-g6d61a53dd6f5 #1
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   binder_add_device+0x5c/0x9c
   binderfs_binder_device_create+0x690/0x84c
   [...]
   __arm64_sys_mount+0x324/0x3bc

  Allocated by task 632:
   binderfs_binder_device_create+0x168/0x84c
   binder_ctl_ioctl+0xfc/0x184
   [...]
   __arm64_sys_ioctl+0x110/0x150

  Freed by task 649:
   kfree+0xe0/0x338
   binderfs_evict_inode+0x138/0x1dc
   [...]
  ==================================================================

Remove devices from binder_devices before destroying them.

Cc: Li Li <dualli@...gle.com>
Reported-by: syzbot+7015dcf45953112c8b45@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7015dcf45953112c8b45
Fixes: 12d909cac1e1 ("binderfs: add new binder devices to binder_devices")
Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
---
 drivers/android/binderfs.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index bc6bae76ccaf..94c6446604fc 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -274,6 +274,7 @@ static void binderfs_evict_inode(struct inode *inode)
 	mutex_unlock(&binderfs_minors_mutex);
 
 	if (refcount_dec_and_test(&device->ref)) {
+		hlist_del_init(&device->hlist);
 		kfree(device->context.name);
 		kfree(device);
 	}
-- 
2.48.1.362.g079036d154-goog