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

[Dmitry Vyukov <dvyukov@google.com>]

On Fri, Sep 20, 2019 at 12:02 PM Johan Hovold <johan@kernel.org> wrote:
>
> On Fri, Sep 20, 2019 at 02:20:00AM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot has tested the proposed patch but the reproducer still triggered
> > crash:
> > KASAN: use-after-free Read in adu_interrupt_in_callback
> >
> > ==================================================================
> > BUG: KASAN: use-after-free in __lock_acquire+0x302a/0x3b50
> > kernel/locking/lockdep.c:3753
> > Read of size 8 at addr ffff8881cd4d0358 by task kworker/0:6/3051
> >
> > CPU: 0 PID: 3051 Comm: kworker/0:6 Not tainted 5.3.0-rc2+ #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Workqueue: usb_hub_wq hub_event
> > Call Trace:
> >   <IRQ>
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0xca/0x13e lib/dump_stack.c:113
> >   print_address_description+0x6a/0x32c mm/kasan/report.c:351
> >   __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:482
> >   kasan_report+0xe/0x12 mm/kasan/common.c:612
> >   __lock_acquire+0x302a/0x3b50 kernel/locking/lockdep.c:3753
> >   lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4412
> >   __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
> >   _raw_spin_lock_irqsave+0x32/0x50 kernel/locking/spinlock.c:159
> >   adu_interrupt_in_callback+0x77/0x380 drivers/usb/misc/adutux.c:163
> >   __usb_hcd_giveback_urb+0x1f2/0x470 drivers/usb/core/hcd.c:1757
> >   usb_hcd_giveback_urb+0x368/0x420 drivers/usb/core/hcd.c:1822
> >   dummy_timer+0x120f/0x2fa2 drivers/usb/gadget/udc/dummy_hcd.c:1965
> >   call_timer_fn+0x179/0x650 kernel/time/timer.c:1322
> >   expire_timers kernel/time/timer.c:1366 [inline]
> >   __run_timers kernel/time/timer.c:1685 [inline]
> >   __run_timers kernel/time/timer.c:1653 [inline]
> >   run_timer_softirq+0x5cc/0x14b0 kernel/time/timer.c:1698
> >   __do_softirq+0x221/0x912 kernel/softirq.c:292
> >   invoke_softirq kernel/softirq.c:373 [inline]
> >   irq_exit+0x178/0x1a0 kernel/softirq.c:413
> >   exiting_irq arch/x86/include/asm/apic.h:537 [inline]
> >   smp_apic_timer_interrupt+0x12f/0x500 arch/x86/kernel/apic/apic.c:1095
> >   apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:828
> >   </IRQ>
> > RIP: 0010:arch_local_irq_restore arch/x86/include/asm/irqflags.h:85 [inline]
> > RIP: 0010:console_unlock+0xa2a/0xc40 kernel/printk/printk.c:2471
> > Code: 00 89 ee 48 c7 c7 20 88 d3 86 e8 81 ad 03 00 65 ff 0d 72 a1 d9 7e e9
> > db f9 ff ff e8 70 a1 15 00 e8 1b cb 1a 00 ff 74 24 30 9d <e9> 18 fe ff ff
> > e8 5c a1 15 00 48 8d 7d 08 48 89 f8 48 c1 e8 03 42
> > RSP: 0018:ffff8881cd20f200 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13
> > RAX: 0000000000000007 RBX: 0000000000000200 RCX: 0000000000000006
> > RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff8881ccd8d044
> > RBP: 0000000000000000 R08: ffff8881ccd8c800 R09: fffffbfff11acd91
> > R10: fffffbfff11acd90 R11: ffffffff88d66c87 R12: 0000000000000047
> > R13: dffffc0000000000 R14: ffffffff82909100 R15: ffffffff87077190
> >   vprintk_emit+0x171/0x3e0 kernel/printk/printk.c:1986
> >   vprintk_func+0x75/0x113 kernel/printk/printk_safe.c:386
> >   printk+0xba/0xed kernel/printk/printk.c:2046
> >   really_probe.cold+0x81/0x13a drivers/base/dd.c:616
> >   driver_probe_device+0x101/0x1b0 drivers/base/dd.c:709
> >   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:816
> >   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
> >   __device_attach+0x217/0x360 drivers/base/dd.c:882
> >   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
> >   device_add+0xae6/0x16f0 drivers/base/core.c:2114
> >   usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
> >   generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
> >   usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
> >   really_probe+0x281/0x650 drivers/base/dd.c:548
> >   driver_probe_device+0x101/0x1b0 drivers/base/dd.c:709
> >   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:816
> >   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
> >   __device_attach+0x217/0x360 drivers/base/dd.c:882
> >   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
> >   device_add+0xae6/0x16f0 drivers/base/core.c:2114
> >   usb_new_device.cold+0x6a4/0xe79 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+0x1b5c/0x3640 drivers/usb/core/hub.c:5441
> >   process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
> >   worker_thread+0x96/0xe20 kernel/workqueue.c:2415
> >   kthread+0x318/0x420 kernel/kthread.c:255
> >   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> >
> > Allocated by task 3051:
> >   save_stack+0x1b/0x80 mm/kasan/common.c:69
> >   set_track mm/kasan/common.c:77 [inline]
> >   __kasan_kmalloc mm/kasan/common.c:487 [inline]
> >   __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:460
> >   kmalloc include/linux/slab.h:552 [inline]
> >   kzalloc include/linux/slab.h:748 [inline]
> >   adu_probe+0x7d/0x6e0 drivers/usb/misc/adutux.c:660
> >   usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
> >   really_probe+0x281/0x650 drivers/base/dd.c:548
> >   driver_probe_device+0x101/0x1b0 drivers/base/dd.c:709
> >   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:816
> >   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
> >   __device_attach+0x217/0x360 drivers/base/dd.c:882
> >   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
> >   device_add+0xae6/0x16f0 drivers/base/core.c:2114
> >   usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
> >   generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
> >   usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
> >   really_probe+0x281/0x650 drivers/base/dd.c:548
> >   driver_probe_device+0x101/0x1b0 drivers/base/dd.c:709
> >   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:816
> >   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
> >   __device_attach+0x217/0x360 drivers/base/dd.c:882
> >   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
> >   device_add+0xae6/0x16f0 drivers/base/core.c:2114
> >   usb_new_device.cold+0x6a4/0xe79 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+0x1b5c/0x3640 drivers/usb/core/hub.c:5441
> >   process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
> >   worker_thread+0x96/0xe20 kernel/workqueue.c:2415
> >   kthread+0x318/0x420 kernel/kthread.c:255
> >   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> >
> > Freed by task 3051:
> >   save_stack+0x1b/0x80 mm/kasan/common.c:69
> >   set_track mm/kasan/common.c:77 [inline]
> >   __kasan_slab_free+0x130/0x180 mm/kasan/common.c:449
> >   slab_free_hook mm/slub.c:1423 [inline]
> >   slab_free_freelist_hook mm/slub.c:1470 [inline]
> >   slab_free mm/slub.c:3012 [inline]
> >   kfree+0xe4/0x2f0 mm/slub.c:3953
> >   adu_probe+0x5de/0x6e0 drivers/usb/misc/adutux.c:750
> >   usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
> >   really_probe+0x281/0x650 drivers/base/dd.c:548
> >   driver_probe_device+0x101/0x1b0 drivers/base/dd.c:709
> >   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:816
> >   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
> >   __device_attach+0x217/0x360 drivers/base/dd.c:882
> >   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
> >   device_add+0xae6/0x16f0 drivers/base/core.c:2114
> >   usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
> >   generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
> >   usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
> >   really_probe+0x281/0x650 drivers/base/dd.c:548
> >   driver_probe_device+0x101/0x1b0 drivers/base/dd.c:709
> >   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:816
> >   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
> >   __device_attach+0x217/0x360 drivers/base/dd.c:882
> >   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
> >   device_add+0xae6/0x16f0 drivers/base/core.c:2114
> >   usb_new_device.cold+0x6a4/0xe79 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+0x1b5c/0x3640 drivers/usb/core/hub.c:5441
> >   process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
> >   worker_thread+0x96/0xe20 kernel/workqueue.c:2415
> >   kthread+0x318/0x420 kernel/kthread.c:255
> >   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>
> This looks like a separate issue, which should be fixed by a separate
> patch. Not sure how to tell syzbot that. Dmitry?

There is no way, but also no need. There is nothing it can do with that info.
If you think it's a separate one and you fixed the first one, mail the
patch with the first fix.
Optionally, you can fix the second one as well, and then ask it to
test a patch with 2 fixes (but you will need either to squash them or
point to a git tree with both commits).

> There's is indeed another bug in the driver, which could lead to crashes
> in the completion handler after clearing the struct usb_device pointer,
> but possibly also to the above use-after-free if a new device is probed
> immediately after a disconnect.
>
> The below patch addresses both bugs, let's see if that helps.
>
> #syz test: https://github.com/google/kasan.git e96407b4
>
> Johan
>
> From c68eda0c6aae5b233fbd583afbfd3ea15acbc62f Mon Sep 17 00:00:00 2001
> From: Johan Hovold <johan@kernel.org>
> Date: Thu, 19 Sep 2019 11:48:38 +0200
> Subject: [PATCH] USB: adutux: fix use-after-free on disconnect + more
>
> FIXME: separate stopping URBs
>
> The driver was clearing its struct usb_device pointer, which it uses as
> an inverted disconnected flag, before deregistering the character device
> and without serialising against racing release().
>
> This could lead to a use-after-free if a racing release() callback
> observes the cleared pointer and frees the driver data before
> disconnect() is finished with it.
>
> This could also lead to NULL-pointer dereferences in a racing open().
>
> Fixes: f08812d5eb8f ("USB: FIx locks and urb->status in adutux (updated)")
> Reported-by: syzbot+0243cb250a51eeefb8cc@syzkaller.appspotmail.com
> Cc: stable <stable@vger.kernel.org>     # 2.6.24
> Signed-off-by: Johan Hovold <johan@kernel.org>
> ---
>  drivers/usb/misc/adutux.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/misc/adutux.c b/drivers/usb/misc/adutux.c
> index 344d523b0502..a6996772745e 100644
> --- a/drivers/usb/misc/adutux.c
> +++ b/drivers/usb/misc/adutux.c
> @@ -762,14 +762,18 @@ static void adu_disconnect(struct usb_interface *interface)
>
>         dev = usb_get_intfdata(interface);
>
> -       mutex_lock(&dev->mtx);  /* not interruptible */
> -       dev->udev = NULL;       /* poison */
>         usb_deregister_dev(interface, &adu_class);
> -       mutex_unlock(&dev->mtx);
> +
> +       usb_poison_urb(dev->interrupt_in_urb);
> +       usb_poison_urb(dev->interrupt_out_urb);
>
>         mutex_lock(&adutux_mutex);
>         usb_set_intfdata(interface, NULL);
>
> +       mutex_lock(&dev->mtx);  /* not interruptible */
> +       dev->udev = NULL;       /* poison */
> +       mutex_unlock(&dev->mtx);
> +
>         /* if the device is not opened, then we clean up right now */
>         if (!dev->open_count)
>                 adu_delete(dev);
> --
> 2.23.0
>
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