Re: [PATCH blktests] block/002: delay debugfs directory check

Jens Axboe
2022-04-20T22:44:10Z

On 4/20/22 9:05 AM, Ming Lei wrote:
> On Wed, Apr 20, 2022 at 12:42:14PM +0000, Shinichiro Kawasaki wrote:
>> On Apr 20, 2022 / 17:34, Ming Lei wrote:
>>> On Wed, Apr 20, 2022 at 01:59:11PM +0900, Shin'ichiro Kawasaki wrote:
>>>> The test case block/002 checks that device removal during blktrace run
>>>> does not leak debugfs directory. The Linux kernel commit 0a9a25ca7843
>>>> ("block: let blkcg_gq grab request queue's refcnt") triggered failure of
>>>> the test case. The commit delayed queue release and debugfs directory
>>>> removal then the test case checks directory existence too early. To
>>>> avoid this false-positive failure, delay the directory existence check.
>>>>
>>>> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
>>>> ---
>>>> tests/block/002 | 1 +
>>>> 1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/tests/block/002 b/tests/block/002
>>>> index 9b183e7..8061c91 100755
>>>> --- a/tests/block/002
>>>> +++ b/tests/block/002
>>>> @@ -29,6 +29,7 @@ test() {
>>>> echo "debugfs directory deleted with blktrace active"
>>>> fi
>>>> { kill $!; wait; } >/dev/null 2>/dev/null
>>>> + sleep 0.5
>>>> if [[ -d /sys/kernel/debug/block/${SCSI_DEBUG_DEVICES[0]} ]]; then
>>>> echo "debugfs directory leaked"
>>>> fi
>>>
>>> Hello,
>>>
>>> Jens has merged Yu Kuai's fix[1], so I think it won't be triggered now.
>>>
>>>
>>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=block-5.18&id=a87c29e1a85e64b28445bb1e80505230bf2e3b4b
>>
>> Hi Ming, I applied the patch above on top of v5.18-rc3 and ran block/002.
>> Unfortunately, it failed with a new symptom with KASAN use-after-free [2]. I
>> ran block/002 with linux-block/block-5.18 branch tip with git hash a87c29e1a85e
>> and got the same KASAN uaf. Reverting the patch from the linux-block/block-5.18
>> branch, the KASAN uaf disappears (Still block/002 fails). Regarding block/002,
>> it looks the patch made the failure symptom worse.
>
> Hi Shinichiro,
>
> Looks Yu Kuai's patch has other problem, can you drop that patch and
> apply & test the attached patch?
>
> Jens, looks the patch of "blk-mq: fix possible creation failure for
> 'debugfs_dir'" isn't ready to go, can you drop it first from
> block-5.18?

Dropped, thanks Ming.

--
Jens Axboe