From: Bart Van Assche <bvanassche@acm.org>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: axboe@kernel.dk, viro@zeniv.linux.org.uk,
gregkh@linuxfoundation.org, rostedt@goodmis.org,
mingo@redhat.com, jack@suse.cz, ming.lei@redhat.com,
nstange@suse.de, akpm@linux-foundation.org, mhocko@suse.com,
yukuai3@huawei.com, linux-block@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Omar Sandoval <osandov@fb.com>,
Hannes Reinecke <hare@suse.com>, Michal Hocko <mhocko@kernel.org>,
syzbot+603294af2d01acfdd6da@syzkaller.appspotmail.com
Subject: Re: [PATCH v2 03/10] blktrace: fix debugfs use after free
Date: Sun, 19 Apr 2020 17:38:59 -0700 [thread overview]
Message-ID: <b77a39c1-6010-24a4-0815-2f26664b6208@acm.org> (raw)
In-Reply-To: <20200420000436.GI11244@42.do-not-panic.com>
On 4/19/20 5:04 PM, Luis Chamberlain wrote:
> On Sun, Apr 19, 2020 at 02:55:42PM -0700, Bart Van Assche wrote:
>> On 4/19/20 12:45 PM, Luis Chamberlain wrote:
>>> +int __must_check blk_queue_debugfs_register(struct request_queue *q)
>>> +{
>>> + struct dentry *dir = NULL;
>>> +
>>> + /* This can happen if we have a bug in the lower layers */
>>
>> What does "this" refer to? Which layers does "lower layers" refer to? Most
>> software developers consider a module that calls directly into another
>> module as a higher layer (callbacks through function pointers do not count;
>> see also https://en.wikipedia.org/wiki/Modular_programming). According to
>> that definition block drivers are a software layer immediately above the
>> block layer core.
>>
>> How about changing that comment into the following to make it unambiguous
>> (if this is what you meant)?
>>
>> /*
>> * Check whether the debugfs directory already exists. This can
>> * only happen as the result of a bug in a block driver.
>> */
>
> But I didn't mean on a block driver. I meant the block core. In our
> case, the async request_queue removal is an example. There is nothing
> that block drivers could have done to help much with that.
>
> I could just change "lower layers" to "block layer" ?
That sounds good to me.
>> Independent of what the purpose of the above code is, can that code be
>> rewritten such that it does not depend on the details of how names are
>> assigned to disks and partitions? Would disk_get_part() be useful here?
>
> I did try, but couldn't figure out a way. I'll keep looking but likewise
> let me know if you find a way.
How about making blk_trace_setup() pass the result of the following
expression as an additional argument to blk_trace_setup():
bdev != bdev->bd_contains
I think that is a widely used approach to verify after a block device
has been opened whether or not 'bdev' refers to a partition (bdev !=
bdev->bd_contains means that 'bdev' represents a partition).
Thanks,
Bart.
next prev parent reply other threads:[~2020-04-20 0:39 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-19 19:45 [PATCH v2 00/10] block: fix blktrace debugfs use after free Luis Chamberlain
2020-04-19 19:45 ` [PATCH v2 01/10] block: move main block debugfs initialization to its own file Luis Chamberlain
2020-04-19 21:06 ` Bart Van Assche
2020-04-19 19:45 ` [PATCH v2 02/10] blktrace: move blktrace debugfs creation to helper function Luis Chamberlain
2020-04-19 21:11 ` Bart Van Assche
2020-04-22 7:12 ` Christoph Hellwig
2020-04-19 19:45 ` [PATCH v2 03/10] blktrace: fix debugfs use after free Luis Chamberlain
2020-04-19 21:55 ` Bart Van Assche
2020-04-20 0:04 ` Luis Chamberlain
2020-04-20 0:38 ` Bart Van Assche [this message]
2020-04-20 18:46 ` Luis Chamberlain
2020-04-20 20:16 ` Greg KH
2020-04-20 20:41 ` Luis Chamberlain
2020-04-21 7:00 ` Greg KH
2020-04-22 7:28 ` Luis Chamberlain
2020-04-22 9:43 ` Ming Lei
2020-04-22 10:31 ` Luis Chamberlain
2020-04-24 23:47 ` Luis Chamberlain
2020-04-22 7:29 ` Christoph Hellwig
2020-04-22 7:34 ` Luis Chamberlain
2020-04-22 7:27 ` Christoph Hellwig
2020-04-22 7:48 ` Luis Chamberlain
2020-04-22 8:10 ` Christoph Hellwig
2020-04-22 8:26 ` Luis Chamberlain
2020-04-19 19:45 ` [PATCH v2 04/10] block: revert back to synchronous request_queue removal Luis Chamberlain
2020-04-19 22:23 ` Bart Van Assche
2020-04-20 18:59 ` Luis Chamberlain
2020-04-20 21:11 ` Bart Van Assche
2020-04-20 21:51 ` Luis Chamberlain
2020-04-19 19:45 ` [PATCH v2 05/10] blktrace: upgrade warns to BUG_ON() on unexpected circmunstances Luis Chamberlain
2020-04-19 22:50 ` Bart Van Assche
2020-04-19 23:07 ` Luis Chamberlain
2020-04-20 23:20 ` Steven Rostedt
2020-04-19 19:45 ` [PATCH v2 06/10] blk-debugfs: upgrade warns to BUG_ON() if directory is already found Luis Chamberlain
2020-04-20 11:36 ` Greg KH
2020-04-25 11:43 ` [blk] 90d38c0e30: kernel_BUG_at_block/blk-debugfs.c kernel test robot
2020-04-19 19:45 ` [PATCH v2 07/10] blktrace: move debugfs file creation to its own function Luis Chamberlain
2020-04-19 22:55 ` Bart Van Assche
2020-04-20 11:37 ` Greg KH
2020-04-19 19:45 ` [PATCH v2 08/10] blktrace: add checks for created debugfs files on setup Luis Chamberlain
2020-04-19 22:57 ` Bart Van Assche
2020-04-19 23:05 ` Luis Chamberlain
2020-04-19 23:17 ` Bart Van Assche
2020-04-20 11:40 ` Greg KH
2020-04-20 18:44 ` Luis Chamberlain
2020-04-20 20:11 ` Greg KH
2020-04-20 20:20 ` Luis Chamberlain
2020-04-21 6:55 ` Greg KH
2020-04-20 11:39 ` Greg KH
2020-04-19 19:45 ` [PATCH v2 09/10] block: panic if block debugfs dir is not created Luis Chamberlain
2020-04-19 23:08 ` Bart Van Assche
2020-04-20 11:38 ` Greg KH
2020-04-19 19:45 ` [PATCH v2 10/10] block: put_device() if device_add() fails Luis Chamberlain
2020-04-19 23:40 ` Bart Van Assche
2020-04-24 22:32 ` Luis Chamberlain
2020-04-25 1:58 ` Bart Van Assche
2020-04-25 2:12 ` Luis Chamberlain
2020-04-19 19:48 ` [PATCH v2 00/10] block: fix blktrace debugfs use after free Luis Chamberlain
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