From: Luis Chamberlain <mcgrof@kernel.org>
To: Bart Van Assche <bvanassche@acm.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
Subject: Re: [PATCH v2 08/10] blktrace: add checks for created debugfs files on setup
Date: Sun, 19 Apr 2020 23:05:37 +0000 [thread overview]
Message-ID: <20200419230537.GG11244@42.do-not-panic.com> (raw)
In-Reply-To: <38240225-e48e-3035-0baa-4929948b23a3@acm.org>
On Sun, Apr 19, 2020 at 03:57:58PM -0700, Bart Van Assche wrote:
> On 4/19/20 12:45 PM, Luis Chamberlain wrote:
> > Even though debugfs can be disabled, enabling BLK_DEV_IO_TRACE will
> > select DEBUG_FS, and blktrace exposes an API which userspace uses
> > relying on certain files created in debugfs. If files are not created
> > blktrace will not work correctly, so we do want to ensure that a
> > blktrace setup creates these files properly, and otherwise inform
> > userspace.
> >
> > Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> > ---
> > kernel/trace/blktrace.c | 8 +++++---
> > 1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> > index 9cc0153849c3..fc32a8665ce8 100644
> > --- a/kernel/trace/blktrace.c
> > +++ b/kernel/trace/blktrace.c
> > @@ -552,17 +552,19 @@ static int blk_trace_create_debugfs_files(struct blk_user_trace_setup *buts,
> > struct dentry *dir,
> > struct blk_trace *bt)
> > {
> > - int ret = -EIO;
> > -
> > bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt,
> > &blk_dropped_fops);
> > + if (!bt->dropped_file)
> > + return -ENOMEM;
> > bt->msg_file = debugfs_create_file("msg", 0222, dir, bt, &blk_msg_fops);
> > + if (!bt->msg_file)
> > + return -ENOMEM;
> > bt->rchan = relay_open("trace", dir, buts->buf_size,
> > buts->buf_nr, &blk_relay_callbacks, bt);
> > if (!bt->rchan)
> > - return ret;
> > + return -EIO;
> > return 0;
> > }
>
> I should have had a look at this patch before I replied to the previous
> patch.
>
> Do you agree that the following code can be triggered by
> debugfs_create_file() and also that debugfs_create_file() never returns
> NULL?
If debugfs is enabled, and not that we know it is in this blktrace code,
as we select it, it can return ERR_PTR(-ERROR) if an error occurs.
Luis
next prev parent reply other threads:[~2020-04-19 23:05 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
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 [this message]
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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