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

[Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>]

On Apr 20, 2022 / 23:05, 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?

Sure. With the patch, kernel message is clean. But I still observe the test case
failure:

block/002 (remove a device while running blktrace)           [failed]
    runtime  1.276s  ...  1.241s
    --- tests/block/002.out     2022-04-14 11:29:04.760295898 +0900
    +++ /home/shin/blktests/results/nodev/block/002.out.bad   2022-04-21 08:40:01.776511887 +0900
    @@ -1,2 +1,3 @@
     Running block/002
    +debugfs directory deleted with blktrace active
     Test complete

Before applying the patch, the blktests failure message was as follows:

block/002 (remove a device while running blktrace)           [failed]
    runtime    ...  1.570s
    --- tests/block/002.out     2022-04-16 03:58:14.627621791 +0900
    +++ /home/shin/blktests/results/nodev/block/002.out.bad   2022-04-16 04:14:35.471134592 +0900
    @@ -1,2 +1,3 @@
     Running block/002
    +debugfs directory leaked
     Test complete

-- 
Best Regards,
Shin'ichiro Kawasaki