linux-kernel - Re: [lkp] [kallsyms] bf2d2b07db: kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] general protection fault: 0000 [#1] PREEMPT PREEMPT KASANKASAN

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Date:	Mon, 1 Feb 2016 19:48:59 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	kernel test robot <ying.huang@...ux.intel.com>
Cc:	Ard Biesheuvel <ard.biesheuvel@...aro.org>, lkp@...org,
	LKML <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Michal Marek <mmarek@...e.cz>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Kees Cook <keescook@...omium.org>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>
Subject: Re: [lkp] [kallsyms] bf2d2b07db: kasan: GPF could be caused by
 NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1]
 general protection fault: 0000 [#1] PREEMPT PREEMPT KASANKASAN

On 02/01/2016 04:20 PM, Andrew Morton wrote:
> On Thu, 28 Jan 2016 09:12:15 +0800 kernel test robot <ying.huang@...ux.intel.com> wrote:
>
>> FYI, we noticed the below changes on
>>
>> https://git.linaro.org/people/ard.biesheuvel/linux-arm arm64-kaslr-v4a
>> commit bf2d2b07db19001ae0bd55826025b0ba47fae0c2 ("kallsyms: add support for relative offsets in kallsyms address table")
>>
>>
>> +-----------------------------------------------------------+------------+------------+
>> |                                                           | 2c4d21df0f | bf2d2b07db |
>> +-----------------------------------------------------------+------------+------------+
>> | boot_successes                                            | 10         | 0          |
>> | boot_failures                                             | 6          | 36         |
>> | Kernel_panic-not_syncing:Attempted_to_kill_init!exitcode= | 2          |            |
>> | IP-Config:Auto-configuration_of_network_failed            | 4          |            |
>> | general_protection_fault:#[##]PREEMPT_PREEMPT_KASANKASAN  | 0          | 36         |
>> | general_protection_fault:#[##]                            | 0          | 36         |
>> | BUG:kernel_boot_hang                                      | 0          | 36         |
>> +-----------------------------------------------------------+------------+------------+
>>
>>
>>
>> [    0.281636] kasan: CONFIG_KASAN_INLINE enabled
>>
>> [    0.282416] kasan: GPF could be caused by NULL-ptr deref or user memory access
>> [    0.282416] kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] general protection fault: 0000 [#1] PREEMPT PREEMPT KASANKASAN
>>
>> [    0.284561] Modules linked in:
>> [    0.284561] Modules linked in:
>>
>> [    0.285136] CPU: 0 PID: 1 Comm: swapper Not tainted 4.5.0-rc1-00036-gbf2d2b0 #1
>> [    0.285136] CPU: 0 PID: 1 Comm: swapper Not tainted 4.5.0-rc1-00036-gbf2d2b0 #1
>> [    0.286438] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
>> [    0.286438] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
>> [    0.288000] task: ffff88000fcb0000 ti: ffff88000fcb8000 task.ti: ffff88000fcb8000
>> [    0.288000] task: ffff88000fcb0000 ti: ffff88000fcb8000 task.ti: ffff88000fcb8000
>> [    0.289287] RIP: 0010:[<ffffffff8120688c>]
>
> I'm not sufficiently familiar with KASAN to be able to interpret this.
> Perhaps Andrey can shed some light?
>
> The lack of symbol decoding is a problem.
>
> CONFIG_KALLSYMS=y
> CONFIG_KALLSYMS_ALL=y
> CONFIG_KALLSYMS_BASE_RELATIVE=y
>
> It should be there.  Perhaps it is not because this error is itself
> (possibly) related to kallsyms changes?
>

Probably. I had seen something similar (crash and no symbols) with an earlier version of the patch,
if the symbols were not created. There might be a message in the log, indicating that kallsyms
failed to generate the symbols.

Guenter