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

[Johan Hovold]

On Mon, Sep 30, 2019 at 03:39:15PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    2994c077 usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=173b5acd600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=69ddefac6929256a
> dashboard link: https://syzkaller.appspot.com/bug?extid=e29b17e5042bbc56fae9
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10ec8e19600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=107ad813600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+e29b17e5042bbc56fae9@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> mcba_usb 1-1:0.180 can1: Failed to send cmd (169)
> mcba_usb 1-1:0.180: Microchip CAN BUS Analyzer connected
> usb 1-1: USB disconnect, device number 2
> mcba_usb 1-1:0.95 can0: device disconnected
> ==================================================================
> BUG: KASAN: use-after-free in __lock_acquire+0x3377/0x3eb0  
> kernel/locking/lockdep.c:3828
> Read of size 8 at addr ffff8881d2e98f48 by task kworker/0:1/12
> 
> CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.3.0+ #0
> 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.constprop.0+0x36/0x50 mm/kasan/report.c:374
>   __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:506
>   kasan_report+0xe/0x12 mm/kasan/common.c:634
>   __lock_acquire+0x3377/0x3eb0 kernel/locking/lockdep.c:3828
>   lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4487
>   __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
>   _raw_spin_lock_irq+0x2d/0x40 kernel/locking/spinlock.c:167
>   spin_lock_irq include/linux/spinlock.h:363 [inline]
>   usb_kill_anchored_urbs+0x1e/0x110 drivers/usb/core/urb.c:787
>   mcba_urb_unlink drivers/net/can/usb/mcba_usb.c:711 [inline]
>   mcba_usb_disconnect+0xd6/0xe4 drivers/net/can/usb/mcba_usb.c:881
>   usb_unbind_interface+0x1bd/0x8a0 drivers/usb/core/driver.c:423
>   __device_release_driver drivers/base/dd.c:1134 [inline]
>   device_release_driver_internal+0x42f/0x500 drivers/base/dd.c:1165
>   bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:532
>   device_del+0x420/0xb10 drivers/base/core.c:2375
>   usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
>   usb_disconnect+0x284/0x8d0 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+0x1454/0x3640 drivers/usb/core/hub.c:5441
>   process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
>   process_scheduled_works kernel/workqueue.c:2331 [inline]
>   worker_thread+0x7ab/0xe20 kernel/workqueue.c:2417
>   kthread+0x318/0x420 kernel/kthread.c:255
>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> 
> The buggy address belongs to the page:
> page:ffffea00074ba600 refcount:0 mapcount:-128 mapping:0000000000000000  
> index:0x0
> flags: 0x200000000000000()
> raw: 0200000000000000 ffffea0007479208 ffff88821fffac18 0000000000000000
> raw: 0000000000000000 0000000000000003 00000000ffffff7f 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>   ffff8881d2e98e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>   ffff8881d2e98e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> > ffff8881d2e98f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>                                                ^
>   ffff8881d2e98f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>   ffff8881d2e99000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ==================================================================

Fix posted

	https://lkml.kernel.org/r/20191001102914.4567-2-johan@xxxxxxxxxx

Johan