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Subject: Re: [PATCH 5.17 000/772] 5.17.14-rc1 review
From:   Coly Li <colyli@suse.de>
In-Reply-To: <20220618113703.GA10888@duo.ucw.cz>
Date:   Sat, 18 Jun 2022 19:57:01 +0800
Cc:     Pavel Machek <pavel@denx.de>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
        baijiaju1990@gmail.com, oslab@tsinghua.edu.cn,
        Jens Axboe <axboe@kernel.dk>, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org, torvalds@linux-foundation.org,
        akpm@linux-foundation.org, linux@roeck-us.net, shuah@kernel.org,
        patches@kernelci.org, lkft-triage@lists.linaro.org,
        jonathanh@nvidia.com, f.fainelli@gmail.com,
        sudipm.mukherjee@gmail.com, slade@sladewatkins.com,
        Daniel Latypov <dlatypov@google.com>,
        Brendan Higgins <brendanhiggins@google.com>,
        kunit-dev@googlegroups.com,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>
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References: <20220607164948.980838585@linuxfoundation.org>
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To:     Pavel Machek <pavel@ucw.cz>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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> 2022=E5=B9=B46=E6=9C=8818=E6=97=A5 19:37=EF=BC=8CPavel Machek =
<pavel@ucw.cz> =E5=86=99=E9=81=93=EF=BC=9A
>=20
> Hi!
>=20
>>>>   Fixes: bc082a55d25c ("bcache: fix inaccurate io state for =
detached
>>> ...
>>>=20
>>>> +++ b/drivers/md/bcache/request.c
>>>> @@ -1107,6 +1107,12 @@ static void detached_dev_do_request(struct
>>>> bcache_device *d, struct bio *bio,
>>>>        * which would call closure_get(&dc->disk.cl)
>>>>        */
>>>>       ddip =3D kzalloc(sizeof(struct detached_dev_io_private), =
GFP_NOIO);
>>>> +       if (!ddip) {
>>>> +               bio->bi_status =3D BLK_STS_RESOURCE;
>>>> +               bio->bi_end_io(bio);
>>>> +               return;
>>>> +       }
>>>> +
>>>>       ddip->d =3D d;
>>>>       /* Count on the bcache device */
>>>>       ddip->orig_bdev =3D orig_bdev;
>>>>=20
>>>=20
>>> So... for patch to make any difference, memory allocation has to =
fail
>>> and ddip has to be NULL.
>>>=20
>>> Before the patch, it would oops in "ddip->d =3D d;". With the patch, =
you
>>> do some kind of error handling. Even if it is buggy, it should not =
do
>>> more harm than immediate oops.
>>=20
>> I just receive this single email and don=E2=80=99t have any idea for =
the context and what the problem is. Where can I see the whole =
conversation?
>>=20
>=20
> Discussion happened on stable@vger.kernel.org mailing lists, archives
> should be easily available. Copy went to lkml, too.

Hi Pavel and Greg,

Thanks for the hint, I see the context. I cannot tell the direct reason =
of the kfence regression, but it is worthy to have this patch in,
- commit 7d6b902ea0e0 ("bcache: memset on stack variables in =
bch_btree_check() and bch_sectors_dirty_init()=E2=80=9D)

I am not sure whether it is directly related to the kfence issue, it =
corrects potential unexpected stack state in some condition. Hope it may =
help a bit.

Thanks.

Coly Li=