Hi Mathias,

On Sat, Jun 30, 2018 at 10:07:04PM +0100, Sudip Mukherjee wrote:
> Hi Mathias,
> 
> On Fri, Jun 29, 2018 at 02:41:13PM +0300, Mathias Nyman wrote:
> > On 27.06.2018 14:59, Sudip Mukherjee wrote:
> > > > > Can you share a bit more details on the platform you are using, and what types of test you are running.
> > > > 
<snip>
> Then to track what is going on, I added the slub debugging and :(
> I have attached part of dmesg for you to check.
> Will appreciate your help in finding out the problem.

I did some more debugging. Tested with a KASAN enabled kernel and that
shows the problem. The report is attached.

To my understanding:

btusb_work() is calling usb_set_interface() with alternate = 0. which
again calls usb_hcd_alloc_bandwidth() and that frees the rings by
xhci_free_endpoint_ring(). But then usb_set_interface() continues and
calls usb_disable_interface() -> usb_hcd_flush_endpoint()->unlink1()->
xhci_urb_dequeue() which at the end gives the command to stop endpoint.

In all the cycles I have tested I see that only in the fail case
handle_cmd_completion() gets called, but in the cycles where the error
is not there handle_cmd_completion() is not called with that command.

I am not sure what is happening, and you are the best person to understand
what is happening. :)

But for now (untill you are back from holiday and suggest a proper solution),
I made a hacky patch (attached) which is working and I donot get any
corruption after that. Both KASAN and slub debug are also happy.

So, now waiting for you to analyze what is going on and suggest a proper
fix.

Thanks in advance.
---
Regards
Sudip
[  236.814156] ==================================================================
[  236.814187] BUG: KASAN: use-after-free in xhci_trb_virt_to_dma+0x2e/0x74 [xhci_hcd]
[  236.814193] Read of size 8 at addr ffff8800789329c8 by task weston/138

[  236.814203] CPU: 0 PID: 138 Comm: weston Tainted: G     U  W  O    4.14.47-20180606+ #7
[  236.814206] Hardware name: xxx, BIOS 2017.01-00087-g43e04de 08/30/2017
[  236.814209] Call Trace:
[  236.814214]  <IRQ>
[  236.814226]  dump_stack+0x46/0x59
[  236.814238]  print_address_description+0x6b/0x23b
[  236.814255]  ? xhci_trb_virt_to_dma+0x2e/0x74 [xhci_hcd]
[  236.814262]  kasan_report+0x220/0x246
[  236.814278]  xhci_trb_virt_to_dma+0x2e/0x74 [xhci_hcd]
[  236.814294]  trb_in_td+0x3b/0x1cd [xhci_hcd]
[  236.814311]  handle_cmd_completion+0x1181/0x2c9b [xhci_hcd]
[  236.814329]  ? xhci_queue_new_dequeue_state+0x5d9/0x5d9 [xhci_hcd]
[  236.814337]  ? drm_handle_vblank+0x4ec/0x590
[  236.814352]  xhci_irq+0x529/0x3294 [xhci_hcd]
[  236.814362]  ? __accumulate_pelt_segments+0x24/0x33
[  236.814378]  ? finish_td.isra.40+0x223/0x223 [xhci_hcd]
[  236.814384]  ? __accumulate_pelt_segments+0x24/0x33
[  236.814390]  ? __accumulate_pelt_segments+0x24/0x33
[  236.814405]  ? xhci_irq+0x3294/0x3294 [xhci_hcd]
[  236.814412]  __handle_irq_event_percpu+0x149/0x3db
[  236.814421]  handle_irq_event_percpu+0x65/0x109
[  236.814428]  ? __handle_irq_event_percpu+0x3db/0x3db
[  236.814436]  ? ttwu_do_wakeup.isra.18+0x3a2/0x3ce
[  236.814442]  handle_irq_event+0xa8/0x10a
[  236.814449]  handle_edge_irq+0x4b2/0x538
[  236.814458]  handle_irq+0x3e/0x45
[  236.814465]  do_IRQ+0x5c/0x126
[  236.814474]  common_interrupt+0x7a/0x7a
[  236.814478]  </IRQ>
[  236.814483] RIP: 0023:0xf79d3d82
[  236.814486] RSP: 002b:00000000ffc588e8 EFLAGS: 00200282 ORIG_RAX: ffffffffffffffdc
[  236.814493] RAX: 0000000000000000 RBX: 00000000f7bebd5c RCX: 0000000000000000
[  236.814496] RDX: 0000000008d4197c RSI: 0000000000000000 RDI: 00000000f746c020
[  236.814499] RBP: 00000000ffc588e8 R08: 0000000000000000 R09: 0000000000000000
[  236.814503] R10: 0000000000000000 R11: 0000000000200206 R12: 0000000000000000
[  236.814506] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

[  236.814513] Allocated by task 2082:
[  236.814521]  kasan_kmalloc.part.1+0x51/0xc7
[  236.814526]  kmem_cache_alloc_trace+0x178/0x187
[  236.814540]  xhci_segment_alloc.isra.11+0x9d/0x3bf [xhci_hcd]
[  236.814553]  xhci_alloc_segments_for_ring+0x9e/0x176 [xhci_hcd]
[  236.814566]  xhci_ring_alloc.constprop.16+0x197/0x4ba [xhci_hcd]
[  236.814579]  xhci_endpoint_init+0x77a/0x9ba [xhci_hcd]
[  236.814592]  xhci_add_endpoint+0x3bc/0x43b [xhci_hcd]
[  236.814615]  usb_hcd_alloc_bandwidth+0x7ef/0x857 [usbcore]
[  236.814637]  usb_set_interface+0x294/0x681 [usbcore]
[  236.814645]  btusb_work+0x2e6/0x981 [btusb]
[  236.814651]  process_one_work+0x579/0x9e9
[  236.814656]  worker_thread+0x68f/0x804
[  236.814662]  kthread+0x31c/0x32b
[  236.814668]  ret_from_fork+0x35/0x40

[  236.814672] Freed by task 1533:
[  236.814678]  kasan_slab_free+0xb3/0x15e
[  236.814683]  kfree+0x103/0x1a9
[  236.814696]  xhci_ring_free+0x205/0x286 [xhci_hcd]
[  236.814709]  xhci_free_endpoint_ring+0x4d/0x83 [xhci_hcd]
[  236.814722]  xhci_check_bandwidth+0x57b/0x65a [xhci_hcd]
[  236.814743]  usb_hcd_alloc_bandwidth+0x665/0x857 [usbcore]
[  236.814765]  usb_set_interface+0x294/0x681 [usbcore]
[  236.814772]  btusb_work+0x664/0x981 [btusb]
[  236.814777]  process_one_work+0x579/0x9e9
[  236.814782]  worker_thread+0x68f/0x804
[  236.814788]  kthread+0x31c/0x32b
[  236.814793]  ret_from_fork+0x35/0x40

[  236.814799] The buggy address belongs to the object at ffff8800789329c8
 which belongs to the cache kmalloc-64 of size 64
[  236.814804] The buggy address is located 0 bytes inside of
 64-byte region [ffff8800789329c8, ffff880078932a08)
[  236.814806] The buggy address belongs to the page:
[  236.814812] page:ffffea0001e24c80 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
[  236.825813] flags: 0x4000000000008100(slab|head)
[  236.830981] raw: 4000000000008100 0000000000000000 0000000000000000 0000000100130013
[  236.830988] raw: ffffea0000cfbaa0 ffffea00010ddf20 ffff88013b80f640 0000000000000000
[  236.830990] page dumped because: kasan: bad access detected

[  236.830993] Memory state around the buggy address:
[  236.830999]  ffff880078932880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  236.831004]  ffff880078932900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  236.831008] >ffff880078932980: fc fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb
[  236.831011]                                               ^
[  236.831015]  ffff880078932a00: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  236.831019]  ffff880078932a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  236.831021] ==================================================================
[  236.831024] Disabling lock debugging due to kernel taint

From cbbe6dc59ac90a4f2c358de56e58e254320171e0 Mon Sep 17 00:00:00 2001
From: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Date: Tue, 10 Jul 2018 09:50:00 +0100
Subject: [PATCH] hacky solution to mem-corruption

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 drivers/usb/core/message.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 7cd4ec33dbf4..7fdf7a27611d 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1398,7 +1398,8 @@ int usb_set_interface(struct usb_device *dev, int interface, int alternate)
 		remove_intf_ep_devs(iface);
 		usb_remove_sysfs_intf_files(iface);
 	}
-	usb_disable_interface(dev, iface, true);
+	if (!(iface->cur_altsetting && alt))
+		usb_disable_interface(dev, iface, true);
 
 	iface->cur_altsetting = alt;
 
-- 
2.11.0