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* USB: dummy-hcd: Fix failure to give back unlinked URBs
@ 2019-04-18 17:12 ` Alan Stern
  0 siblings, 0 replies; 33+ messages in thread
From: Alan Stern @ 2019-04-18 17:12 UTC (permalink / raw)
  To: Greg KH; +Cc: andreyknvl, gustavo, USB list, syzkaller-bugs

The syzkaller USB fuzzer identified a failure mode in which dummy-hcd
would never give back an unlinked URB.  This causes usb_kill_urb() to
hang, leading to WARNINGs and unkillable threads.

In dummy-hcd, all URBs are given back by the dummy_timer() routine as
it scans through the list of pending URBS.  Failure to give back URBs
can be caused by failure to start or early exit from the scanning
loop.  The code currently has two such pathways: One is triggered when
an unsupported bus transfer speed is encountered, and the other by
exhausting the simulated bandwidth for USB transfers during a frame.

This patch removes those two paths, thereby allowing all unlinked URBs
to be given back in a timely manner.  It adds a check for the bus
speed when the gadget first starts running, so that dummy_timer() will
never thereafter encounter an unsupported speed.  And it prevents the
loop from exiting as soon as the total bandwidth has been used up (the
scanning loop continues, giving back unlinked URBs as they are found,
but not transferring any more data).

Thanks to Andrey Konovalov for manually running the syzkaller fuzzer
to help track down the source of the bug.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: syzbot+d919b0f29d7b5a4994b9@syzkaller.appspotmail.com
CC: <stable@vger.kernel.org>
---


[as1889]


 drivers/usb/gadget/udc/dummy_hcd.c |   19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

Index: usb-devel/drivers/usb/gadget/udc/dummy_hcd.c
===================================================================
--- usb-devel.orig/drivers/usb/gadget/udc/dummy_hcd.c
+++ usb-devel/drivers/usb/gadget/udc/dummy_hcd.c
@@ -979,8 +979,18 @@ static int dummy_udc_start(struct usb_ga
 	struct dummy_hcd	*dum_hcd = gadget_to_dummy_hcd(g);
 	struct dummy		*dum = dum_hcd->dum;
 
-	if (driver->max_speed == USB_SPEED_UNKNOWN)
+	switch (g->speed) {
+	/* All the speeds we support */
+	case USB_SPEED_LOW:
+	case USB_SPEED_FULL:
+	case USB_SPEED_HIGH:
+	case USB_SPEED_SUPER:
+		break;
+	default:
+		dev_err(dummy_dev(dum_hcd), "Unsupported driver max speed %d\n",
+				driver->max_speed);
 		return -EINVAL;
+	}
 
 	/*
 	 * SLAVE side init ... the layer above hardware, which
@@ -1784,9 +1794,10 @@ static void dummy_timer(struct timer_lis
 		/* Bus speed is 500000 bytes/ms, so use a little less */
 		total = 490000;
 		break;
-	default:
+	default:	/* Can't happen */
 		dev_err(dummy_dev(dum_hcd), "bogus device speed\n");
-		return;
+		total = 0;
+		break;
 	}
 
 	/* FIXME if HZ != 1000 this will probably misbehave ... */
@@ -1828,7 +1839,7 @@ restart:
 
 		/* Used up this frame's bandwidth? */
 		if (total <= 0)
-			break;
+			continue;
 
 		/* find the gadget's ep for this request (if configured) */
 		address = usb_pipeendpoint (urb->pipe);

^ permalink raw reply	[flat|nested] 33+ messages in thread
* INFO: task hung in usb_kill_urb
@ 2019-04-12 11:46 syzbot
  2019-04-12 19:46 ` Alan Stern
  0 siblings, 1 reply; 33+ messages in thread
From: syzbot @ 2019-04-12 11:46 UTC (permalink / raw)
  To: andreyknvl, gregkh, gustavo, linux-kernel, linux-usb, syzkaller-bugs

Hello,

syzbot found the following crash on:

HEAD commit:    9a33b369 usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan/tree/usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=14c4c1af200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=23e37f59d94ddd15
dashboard link: https://syzkaller.appspot.com/bug?extid=d919b0f29d7b5a4994b9
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14410dbb200000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12f0acd3200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d919b0f29d7b5a4994b9@syzkaller.appspotmail.com

usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22
usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22
usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22
usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22
usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22
INFO: task kworker/0:2:532 blocked for more than 143 seconds.
       Not tainted 5.1.0-rc4-319354-g9a33b36 #3
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/0:2     D26656   532      2 0x80000000
Workqueue: usb_hub_wq hub_event
Call Trace:
  schedule+0x8f/0x180 kernel/sched/core.c:3562
  usb_kill_urb drivers/usb/core/urb.c:695 [inline]
  usb_kill_urb+0x22a/0x2c0 drivers/usb/core/urb.c:687
  usb_start_wait_urb+0x257/0x4d0 drivers/usb/core/message.c:63
  usb_internal_control_msg drivers/usb/core/message.c:101 [inline]
  usb_control_msg+0x321/0x4a0 drivers/usb/core/message.c:152
usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22
  hub_port_init+0x81d/0x2d30 drivers/usb/core/hub.c:4655
  hub_port_connect drivers/usb/core/hub.c:5021 [inline]
  hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
  port_event drivers/usb/core/hub.c:5350 [inline]
  hub_event+0x11b8/0x3b00 drivers/usb/core/hub.c:5432
  process_one_work+0x90f/0x1580 kernel/workqueue.c:2269
  worker_thread+0x9b/0xe20 kernel/workqueue.c:2415
  kthread+0x313/0x420 kernel/kthread.c:253
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Showing all locks held in the system:
1 lock held by khungtaskd/23:
  #0: 00000000e5b75d53 (rcu_read_lock){....}, at:  
debug_show_all_locks+0x53/0x269 kernel/locking/lockdep.c:5059
5 locks held by kworker/0:2/532:
  #0: 0000000071ab50a3 ((wq_completion)usb_hub_wq){+.+.}, at:  
__write_once_size include/linux/compiler.h:220 [inline]
  #0: 0000000071ab50a3 ((wq_completion)usb_hub_wq){+.+.}, at:  
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
  #0: 0000000071ab50a3 ((wq_completion)usb_hub_wq){+.+.}, at: atomic64_set  
include/asm-generic/atomic-instrumented.h:855 [inline]
  #0: 0000000071ab50a3 ((wq_completion)usb_hub_wq){+.+.}, at:  
atomic_long_set include/asm-generic/atomic-long.h:40 [inline]
  #0: 0000000071ab50a3 ((wq_completion)usb_hub_wq){+.+.}, at: set_work_data  
kernel/workqueue.c:619 [inline]
  #0: 0000000071ab50a3 ((wq_completion)usb_hub_wq){+.+.}, at:  
set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
  #0: 0000000071ab50a3 ((wq_completion)usb_hub_wq){+.+.}, at:  
process_one_work+0x81f/0x1580 kernel/workqueue.c:2240
  #1: 000000004253e0f6 ((work_completion)(&hub->events)){+.+.}, at:  
process_one_work+0x853/0x1580 kernel/workqueue.c:2244
  #2: 00000000eeaa16eb (&dev->mutex){....}, at: device_lock  
include/linux/device.h:1207 [inline]
  #2: 00000000eeaa16eb (&dev->mutex){....}, at: hub_event+0x18a/0x3b00  
drivers/usb/core/hub.c:5378
  #3: 000000004f32b3e5 (&port_dev->status_lock){+.+.}, at: usb_lock_port  
drivers/usb/core/hub.c:2994 [inline]
  #3: 000000004f32b3e5 (&port_dev->status_lock){+.+.}, at: hub_port_connect  
drivers/usb/core/hub.c:5020 [inline]
  #3: 000000004f32b3e5 (&port_dev->status_lock){+.+.}, at:  
hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
  #3: 000000004f32b3e5 (&port_dev->status_lock){+.+.}, at: port_event  
drivers/usb/core/hub.c:5350 [inline]
  #3: 000000004f32b3e5 (&port_dev->status_lock){+.+.}, at:  
hub_event+0x11a3/0x3b00 drivers/usb/core/hub.c:5432
  #4: 00000000bd3d99c8 (hcd->address0_mutex){+.+.}, at:  
hub_port_init+0x1bb/0x2d30 drivers/usb/core/hub.c:4529
1 lock held by rsyslogd/5433:
  #0: 00000000977dfa25 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xe8/0x100  
fs/file.c:801
2 locks held by getty/5523:
  #0: 0000000040ff7945 (&tty->ldisc_sem){++++}, at:  
tty_ldisc_ref_wait+0x27/0x80 drivers/tty/tty_ldisc.c:272
  #1: 000000006c00c4a7 (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x21c/0x1a60 drivers/tty/n_tty.c:2156
2 locks held by getty/5524:
  #0: 00000000cc012e5a (&tty->ldisc_sem){++++}, at:  
tty_ldisc_ref_wait+0x27/0x80 drivers/tty/tty_ldisc.c:272
  #1: 000000001fd3230f (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x21c/0x1a60 drivers/tty/n_tty.c:2156
2 locks held by getty/5525:
  #0: 00000000c53cd960 (&tty->ldisc_sem){++++}, at:  
tty_ldisc_ref_wait+0x27/0x80 drivers/tty/tty_ldisc.c:272
  #1: 00000000e779c4bc (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x21c/0x1a60 drivers/tty/n_tty.c:2156
2 locks held by getty/5526:
  #0: 00000000a6b003b0 (&tty->ldisc_sem){++++}, at:  
tty_ldisc_ref_wait+0x27/0x80 drivers/tty/tty_ldisc.c:272
  #1: 00000000bd516627 (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x21c/0x1a60 drivers/tty/n_tty.c:2156
usb-fuzzer-gadget dummy_udc.0: failed to start USB fuzzer: -22
2 locks held by getty/5527:
  #0: 00000000970614b6 (&tty->ldisc_sem){++++}, at:  
tty_ldisc_ref_wait+0x27/0x80 drivers/tty/tty_ldisc.c:272
  #1: 000000004a83542c (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x21c/0x1a60 drivers/tty/n_tty.c:2156
2 locks held by getty/5528:
  #0: 00000000c9f52a2b (&tty->ldisc_sem){++++}, at:  
tty_ldisc_ref_wait+0x27/0x80 drivers/tty/tty_ldisc.c:272
  #1: 0000000068927d8f (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x21c/0x1a60 drivers/tty/n_tty.c:2156
2 locks held by getty/5529:
  #0: 00000000b02ccb7f (&tty->ldisc_sem){++++}, at:  
tty_ldisc_ref_wait+0x27/0x80 drivers/tty/tty_ldisc.c:272
  #1: 000000001e46199a (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x21c/0x1a60 drivers/tty/n_tty.c:2156

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 23 Comm: khungtaskd Not tainted 5.1.0-rc4-319354-g9a33b36 #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0xe8/0x16e lib/dump_stack.c:113
  nmi_cpu_backtrace.cold+0x48/0x87 lib/nmi_backtrace.c:101
  nmi_trigger_cpumask_backtrace+0x1a6/0x1bd lib/nmi_backtrace.c:62
  trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
  check_hung_uninterruptible_tasks kernel/hung_task.c:204 [inline]
  watchdog+0x98e/0xe20 kernel/hung_task.c:288
  kthread+0x313/0x420 kernel/kthread.c:253
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x2/0x10  
arch/x86/include/asm/irqflags.h:57


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

^ permalink raw reply	[flat|nested] 33+ messages in thread
end of thread, other threads:[~2019-04-23 12:45 UTC | newest]

Thread overview: 33+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <CAAeHK+wDEOpkuh0+OmPra3Yu8ri-8As82CyZ-1KyYC62AJkj1Q@mail.gmail.com>
2019-04-16 15:44 ` INFO: task hung in usb_kill_urb Alan Stern
2019-04-16 15:44   ` Alan Stern
2019-04-16 16:19   ` syzbot
2019-04-16 16:19     ` syzbot
2019-04-16 18:25     ` Alan Stern
2019-04-16 18:25       ` Alan Stern
2019-04-16 19:03       ` syzbot
2019-04-16 19:03         ` syzbot
2019-04-16 21:14         ` Alan Stern
2019-04-16 21:14           ` Alan Stern
2019-04-16 21:53           ` syzbot
2019-04-16 21:53             ` syzbot
2019-04-17 19:09             ` Alan Stern
2019-04-17 19:09               ` Alan Stern
2019-04-17 19:56               ` syzbot
2019-04-17 19:56                 ` syzbot
2019-04-18 12:21               ` Andrey Konovalov
2019-04-18 12:21                 ` Andrey Konovalov
2019-04-17 11:16       ` Andrey Konovalov
2019-04-17 11:16         ` Andrey Konovalov
2019-04-19 18:36         ` UDC hardware for fuzzing [was: Re: INFO: task hung in usb_kill_urb] Alan Stern
2019-04-19 18:36           ` INFO: task hung in usb_kill_urb Alan Stern
2019-04-23 12:44           ` UDC hardware for fuzzing [was: Re: INFO: task hung in usb_kill_urb] Andrey Konovalov
2019-04-23 12:44             ` INFO: task hung in usb_kill_urb Andrey Konovalov
2019-04-18 17:12 USB: dummy-hcd: Fix failure to give back unlinked URBs Alan Stern
2019-04-18 17:12 ` [PATCH] " Alan Stern
  -- strict thread matches above, loose matches on Subject: below --
2019-04-12 11:46 INFO: task hung in usb_kill_urb syzbot
2019-04-12 19:46 ` Alan Stern
2019-04-15 17:48   ` Andrey Konovalov
2019-04-15 18:06     ` Alan Stern
2019-04-15 18:39     ` Gustavo A. R. Silva
2019-04-15 19:00       ` Greg Kroah-Hartman
2019-04-15 19:35         ` Andrey Konovalov

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