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

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Date:   Tue, 7 Jan 2020 14:09:29 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Paul Menzel <pmenzel@...gen.mpg.de>
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

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.
> 

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*

-Mathias