Re: KASAN: use-after-free Read in device_release_driver_internal

[Alan Stern <stern@rowland.harvard.edu>]

On Wed, 7 Aug 2019, syzbot wrote:

> Hello,
> 
> syzbot has tested the proposed patch but the reproducer still triggered  
> crash:
> KASAN: use-after-free Read in device_release_driver_internal
> 
> usb 4-1: USB disconnect, device number 2
> ==================================================================
> BUG: KASAN: use-after-free in __lock_acquire+0x3a5d/0x5340  
> kernel/locking/lockdep.c:3665
> Read of size 8 at addr ffff8881d4a54510 by task kworker/0:3/2876
> 
> CPU: 0 PID: 2876 Comm: kworker/0:3 Not tainted 5.2.0-rc6+ #1
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> Workqueue: usb_hub_wq hub_event
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0xca/0x13e lib/dump_stack.c:113
>   print_address_description+0x67/0x231 mm/kasan/report.c:188
>   __kasan_report.cold+0x1a/0x32 mm/kasan/report.c:317
>   kasan_report+0xe/0x20 mm/kasan/common.c:614
>   __lock_acquire+0x3a5d/0x5340 kernel/locking/lockdep.c:3665
>   lock_acquire+0x100/0x2b0 kernel/locking/lockdep.c:4303
>   __mutex_lock_common kernel/locking/mutex.c:926 [inline]
>   __mutex_lock+0xf9/0x12b0 kernel/locking/mutex.c:1073
>   device_release_driver_internal+0x23/0x4c0 drivers/base/dd.c:1109
>   bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:556
>   device_del+0x460/0xb80 drivers/base/core.c:2274
>   usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
>   usb_disconnect+0x284/0x830 drivers/usb/core/hub.c:2199
>   hub_port_connect drivers/usb/core/hub.c:4949 [inline]
>   hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
>   port_event drivers/usb/core/hub.c:5359 [inline]
>   hub_event+0x13bd/0x3550 drivers/usb/core/hub.c:5441
>   process_one_work+0x905/0x1570 kernel/workqueue.c:2269
>   worker_thread+0x96/0xe20 kernel/workqueue.c:2415
>   kthread+0x30b/0x410 kernel/kthread.c:255
>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> 
> Allocated by task 22:
>   save_stack+0x1b/0x80 mm/kasan/common.c:71
>   set_track mm/kasan/common.c:79 [inline]
>   __kasan_kmalloc mm/kasan/common.c:489 [inline]
>   __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:462
>   kmalloc include/linux/slab.h:547 [inline]
>   kzalloc include/linux/slab.h:742 [inline]
>   usb_set_configuration+0x2c4/0x1670 drivers/usb/core/message.c:1846
>   generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
>   usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
>   really_probe+0x281/0x660 drivers/base/dd.c:509
>   driver_probe_device+0x104/0x210 drivers/base/dd.c:670
>   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777
>   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
>   __device_attach+0x217/0x360 drivers/base/dd.c:843
>   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
>   device_add+0xae6/0x16f0 drivers/base/core.c:2111
>   usb_new_device.cold+0x6a4/0xe61 drivers/usb/core/hub.c:2536
>   hub_port_connect drivers/usb/core/hub.c:5098 [inline]
>   hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
>   port_event drivers/usb/core/hub.c:5359 [inline]
>   hub_event+0x1abd/0x3550 drivers/usb/core/hub.c:5441
>   process_one_work+0x905/0x1570 kernel/workqueue.c:2269
>   worker_thread+0x96/0xe20 kernel/workqueue.c:2415
>   kthread+0x30b/0x410 kernel/kthread.c:255
>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> 
> Freed by task 2876:
>   save_stack+0x1b/0x80 mm/kasan/common.c:71
>   set_track mm/kasan/common.c:79 [inline]
>   __kasan_slab_free+0x130/0x180 mm/kasan/common.c:451
>   slab_free_hook mm/slub.c:1421 [inline]
>   slab_free_freelist_hook mm/slub.c:1448 [inline]
>   slab_free mm/slub.c:2994 [inline]
>   kfree+0xd7/0x280 mm/slub.c:3949
>   device_release+0x71/0x200 drivers/base/core.c:1064
>   kobject_cleanup lib/kobject.c:691 [inline]
>   kobject_release lib/kobject.c:720 [inline]
>   kref_put include/linux/kref.h:65 [inline]
>   kobject_put+0x171/0x280 lib/kobject.c:737
>   put_device+0x1b/0x30 drivers/base/core.c:2210
>   klist_put+0xce/0x170 lib/klist.c:221
>   bus_remove_device+0x3a4/0x4a0 drivers/base/bus.c:552
>   device_del+0x460/0xb80 drivers/base/core.c:2274
>   usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
>   usb_disconnect+0x284/0x830 drivers/usb/core/hub.c:2199
>   hub_port_connect drivers/usb/core/hub.c:4949 [inline]
>   hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
>   port_event drivers/usb/core/hub.c:5359 [inline]
>   hub_event+0x13bd/0x3550 drivers/usb/core/hub.c:5441
>   process_one_work+0x905/0x1570 kernel/workqueue.c:2269
>   worker_thread+0x96/0xe20 kernel/workqueue.c:2415
>   kthread+0x30b/0x410 kernel/kthread.c:255
>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> 
> The buggy address belongs to the object at ffff8881d4a54400
>   which belongs to the cache kmalloc-2k of size 2048
> The buggy address is located 272 bytes inside of
>   2048-byte region [ffff8881d4a54400, ffff8881d4a54c00)
> The buggy address belongs to the page:
> page:ffffea0007529400 refcount:1 mapcount:0 mapping:ffff8881dac02800  
> index:0x0 compound_mapcount: 0
> flags: 0x200000000010200(slab|head)
> raw: 0200000000010200 ffffea000753da00 0000000500000005 ffff8881dac02800
> raw: 0000000000000000 00000000000f000f 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>   ffff8881d4a54400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881d4a54480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8881d4a54500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                           ^
>   ffff8881d4a54580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881d4a54600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> 
> 
> Tested on:
> 
> commit:         6a3599ce usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git
> console output: https://syzkaller.appspot.com/x/log.txt?x=132aca2c600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=700ca426ab83faae
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Maybe this will help pinpoint where the problem occurs.  The kernel log 
should indicate the before and after refcount values for the interface.

Alan Stern

#syz test: https://github.com/google/kasan.git 6a3599ce


Index: usb-devel/drivers/usb/core/driver.c
===================================================================
--- usb-devel.orig/drivers/usb/core/driver.c
+++ usb-devel/drivers/usb/core/driver.c
@@ -358,7 +358,11 @@ static int usb_probe_interface(struct de
 		intf->needs_altsetting0 = 0;
 	}
 
+	dev_info(&intf->dev, "Refcount before probe: %d\n",
+			refcount_read(&intf->dev.kobj.kref.refcount));
 	error = driver->probe(intf, id);
+	dev_info(&intf->dev, "Refcount after probe: %d\n",
+			refcount_read(&intf->dev.kobj.kref.refcount));
 	if (error)
 		goto err;