From: Jens Axboe <axboe@fb.com>
To: Alexander Potapenko <glider@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>,
Kostya Serebryany <kcc@google.com>,
Tahsin Erdogan <tahsin@google.com>,
LKML <linux-kernel@vger.kernel.org>,
<linux-block@vger.kernel.org>
Subject: Re: [PATCH] block: Initialize cfqq->ioprio_class in cfq_get_queue()
Date: Mon, 23 Jan 2017 08:50:16 -0700 [thread overview]
Message-ID: <8399b592-6eab-2c3c-2b6a-28bb2f74e9bd@fb.com> (raw)
In-Reply-To: <CAG_fn=WuZAB_PQgRfgPfUcx-xgYzr_EBqUR5NUBoGufZJEWFrQ@mail.gmail.com>
On 01/23/2017 08:49 AM, Alexander Potapenko wrote:
> On Mon, Jan 23, 2017 at 4:30 PM, Jens Axboe <axboe@fb.com> wrote:
>> On 01/23/2017 07:06 AM, Alexander Potapenko wrote:
>>> KMSAN (KernelMemorySanitizer, a new error detection tool) reports use of
>>> uninitialized memory in cfq_init_cfqq():
>>>
>>> ==================================================================
>>> BUG: KMSAN: use of unitialized memory
>>> ...
>>> Call Trace:
>>> [< inline >] __dump_stack lib/dump_stack.c:15
>>> [<ffffffff8202ac97>] dump_stack+0x157/0x1d0 lib/dump_stack.c:51
>>> [<ffffffff813e9b65>] kmsan_report+0x205/0x360 ??:?
>>> [<ffffffff813eabbb>] __msan_warning+0x5b/0xb0 ??:?
>>> [< inline >] cfq_init_cfqq block/cfq-iosched.c:3754
>>> [<ffffffff8201e110>] cfq_get_queue+0xc80/0x14d0 block/cfq-iosched.c:3857
>>> ...
>>> origin:
>>> [<ffffffff8103ab37>] save_stack_trace+0x27/0x50 arch/x86/kernel/stacktrace.c:67
>>> [<ffffffff813e836b>] kmsan_internal_poison_shadow+0xab/0x150 ??:?
>>> [<ffffffff813e88ab>] kmsan_poison_slab+0xbb/0x120 ??:?
>>> [< inline >] allocate_slab mm/slub.c:1627
>>> [<ffffffff813e533f>] new_slab+0x3af/0x4b0 mm/slub.c:1641
>>> [< inline >] new_slab_objects mm/slub.c:2407
>>> [<ffffffff813e0ef3>] ___slab_alloc+0x323/0x4a0 mm/slub.c:2564
>>> [< inline >] __slab_alloc mm/slub.c:2606
>>> [< inline >] slab_alloc_node mm/slub.c:2669
>>> [<ffffffff813dfb42>] kmem_cache_alloc_node+0x1d2/0x1f0 mm/slub.c:2746
>>> [<ffffffff8201d90d>] cfq_get_queue+0x47d/0x14d0 block/cfq-iosched.c:3850
>>> ...
>>> ==================================================================
>>> (the line numbers are relative to 4.8-rc6, but the bug persists
>>> upstream)
>>>
>>> The uninitialized struct cfq_queue is created by kmem_cache_alloc_node()
>>> and then passed to cfq_init_cfqq(), which accesses cfqq->ioprio_class
>>> before it's initialized.
>>
>> Patch looks fine to me, thanks. Is this a new warning? We don't seem
>> to have changed this path in a while, yet I wonder why this is only
>> surfacing now.
>
> This is because KMSAN is a new tool, it's not in the trunk yet. Nobody
> could see this warning before.
> I don't know if kmemcheck detects this bug (and if anyone is actively
> using it for testing either).
Ah gotcha, I read that as KASAN. Then it makes more sense. Thanks for
clarifying.
--
Jens Axboe
next prev parent reply other threads:[~2017-01-23 15:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-23 14:06 [PATCH] block: Initialize cfqq->ioprio_class in cfq_get_queue() Alexander Potapenko
2017-01-23 15:30 ` Jens Axboe
2017-01-23 15:49 ` Alexander Potapenko
2017-01-23 15:50 ` Jens Axboe [this message]
2017-01-23 16:03 ` Andrey Ryabinin
2017-01-23 16:17 ` Alexander Potapenko
2017-01-23 18:03 ` Jens Axboe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=8399b592-6eab-2c3c-2b6a-28bb2f74e9bd@fb.com \
--to=axboe@fb.com \
--cc=dvyukov@google.com \
--cc=glider@google.com \
--cc=kcc@google.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tahsin@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox