linux-kernel - Re: BUG: KASAN: use-after-free in xhci_trb_virt_to

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Date:   Tue, 7 Jan 2020 16:35:05 +0100
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Greg KH <greg@...ah.com>, Mathias Nyman <mathias.nyman@...el.com>,
        linux-usb@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: BUG: KASAN: use-after-free in
 xhci_trb_virt_to_dma.part.24+0x1c/0x80

Dear Mathias, dear Mika,


On 2020-01-07 13:09, Mathias Nyman wrote:
> On 3.1.2020 13.04, Mika Westerberg wrote:
>> On Thu, Jan 02, 2020 at 03:10:14PM +0100, Paul Menzel wrote:
>>> Mika, as you fixed the other leak, any idea, how to continue from the
>>> kmemleak log below?
>>>
>>> ```
>>> unreferenced object 0xffff8c207a1e1408 (size 8):
>>>    comm "systemd-udevd", pid 183, jiffies 4294667978 (age 752.292s)
>>>    hex dump (first 8 bytes):
>>>      34 01 05 00 00 00 00 00                          4.......
>>>    backtrace:
>>>      [<00000000aea7b46d>] xhci_mem_init+0xcfa/0xec0 [xhci_hcd]
>>
>> There are probably better ways for doing this but you can use objdump
>> for example:
>>
>>    $ objdump -l --prefix-addresses -j .text --disassemble=xhci_mem_init drivers/usb/host/xhci-hcd.ko
>>
>> then find the offset xhci_mem_init+0xcfa. It should show you the line
>> numbers as well if you have compiled your kernel with debug info. This
>> should be close to the line that allocated the memory that was leaked.

Thank you. I actually remembered `script/f2addr2line`.

    $ scripts/faddr2line drivers/usb/host/xhci-hcd.o xhci_mem_init+0xcfa
    xhci_mem_init+0xcfa/0xec0:
    xhci_add_in_port at /mnt/drivers/usb/host/xhci-mem.c:2161
    (inlined by) xhci_setup_port_arrays at /mnt/drivers/usb/host/xhci-mem.c:2309
    (inlined by) xhci_mem_init at /mnt/drivers/usb/host/xhci-mem.c:2538

> Paul, it possible that your xhci controller has several
> supported protocol extended capabilities for usb 3 ports, each
> with their own custom protocol speed ID table.
> 
> xhci driver assumes there is only one custome PSI table per roothub,
> and we will end up allocating the second PSI table on top of the first,
> leaking the first.
> 
> Could you boot with xhci dynamic debug enabled, and show dmesg after boot, add:
> xhci_hcd.dyndbg=+p
> to you kernel cmdline.
> 
> Or as an alternative, show output of:
> 
> sudo cat /sys/kernel/debug/usb/xhci/*/reg-ext-protocol*

`/sys/kernel/debug/` cannot be read by unprivileged users, so the wildcard does
not work with `sudo`.

```
$ sudo ls /sys/kernel/debug/usb/xhci
0000:12:00.0  0000:26:00.3  0000:26:00.4
# cat /sys/kernel/debug/usb/xhci/*/reg-ext-protocol*
EXTCAP_REVISION = 0x03100802
EXTCAP_NAME = 0x20425355
EXTCAP_PORTINFO = 0x00000201
EXTCAP_PORTTYPE = 0x00000000
EXTCAP_REVISION = 0x03000802
EXTCAP_NAME = 0x20425355
EXTCAP_PORTINFO = 0x00000203
EXTCAP_PORTTYPE = 0x00000000
EXTCAP_REVISION = 0x02000802
EXTCAP_NAME = 0x20425355
EXTCAP_PORTINFO = 0x00190a05
EXTCAP_PORTTYPE = 0x00000000
EXTCAP_REVISION = 0x02000402
EXTCAP_NAME = 0x20425355
EXTCAP_PORTINFO = 0x00180401
EXTCAP_PORTTYPE = 0x00000000
EXTCAP_REVISION = 0x03100802
EXTCAP_NAME = 0x20425355
EXTCAP_PORTINFO = 0x10000105
EXTCAP_PORTTYPE = 0x00000000
EXTCAP_MANTISSA1 = 0x00050134
EXTCAP_REVISION = 0x03100802
EXTCAP_NAME = 0x20425355
EXTCAP_PORTINFO = 0x10000106
EXTCAP_PORTTYPE = 0x00000000
EXTCAP_MANTISSA1 = 0x00050134
EXTCAP_REVISION = 0x03100802
EXTCAP_NAME = 0x20425355
EXTCAP_PORTINFO = 0x10000107
EXTCAP_PORTTYPE = 0x00000000
EXTCAP_MANTISSA1 = 0x00050134
EXTCAP_REVISION = 0x03100802
EXTCAP_NAME = 0x20425355
EXTCAP_PORTINFO = 0x10000108
EXTCAP_PORTTYPE = 0x00000000
EXTCAP_MANTISSA1 = 0x00050134
EXTCAP_REVISION = 0x02000402
EXTCAP_NAME = 0x20425355
EXTCAP_PORTINFO = 0x00180101
EXTCAP_PORTTYPE = 0x00000000
EXTCAP_REVISION = 0x03100802
EXTCAP_NAME = 0x20425355
EXTCAP_PORTINFO = 0x10000102
EXTCAP_PORTTYPE = 0x00000000
EXTCAP_MANTISSA1 = 0x00050134
```


Kind regards,

Paul


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