From: Luis Chamberlain <mcgrof@kernel.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: axboe@kernel.dk, viro@zeniv.linux.org.uk, bvanassche@acm.org,
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 v3 4/6] blktrace: fix debugfs use after free
Date: Wed, 29 Apr 2020 11:45:42 +0000 [thread overview]
Message-ID: <20200429114542.GJ11244@42.do-not-panic.com> (raw)
In-Reply-To: <20200429112637.GD21892@infradead.org>
On Wed, Apr 29, 2020 at 04:26:37AM -0700, Christoph Hellwig wrote:
> I can't say I'm a fan of all these long backtraces in commit logs..
>
> > +static struct dentry *blk_debugfs_dir_register(const char *name)
> > +{
> > + return debugfs_create_dir(name, blk_debugfs_root);
> > +}
>
> I don't think we really need this helper.
We don't export blk_debugfs_root, didn't think we'd want to, and
since only a few scew funky drivers would use the struct gendisk
and also support BLKTRACE, I didn't think we'd want to export it
now.
A new block private symbol namespace alright?
> > +void blk_part_debugfs_unregister(struct hd_struct *p)
> > +{
> > + debugfs_remove_recursive(p->debugfs_dir);
> > + p->debugfs_dir = NULL;
> > +}
>
> Why do we need to clear the pointer here?
True, not needed for partition.
> > +#ifdef CONFIG_DEBUG_FS
> > + /* Currently only used by kernel/trace/blktrace.c */
> > + struct dentry *debugfs_dir;
> > +#endif
>
> Does that comment really add value?
I'll nuke it.
> > +static struct dentry *blk_trace_debugfs_dir(struct block_device *bdev,
> > + struct request_queue *q)
> > {
> > + struct hd_struct *p = NULL;
> >
> > + * Some drivers like scsi-generic use a NULL block device. For
> > + * other drivers when bdev != bdev->bd_contain we are doing a blktrace
> > + * on a parition, otherwise we know we are working on the whole
> > + * disk, and for that the request_queue already has its own debugfs_dir.
> > + * which we have been using for other things other than blktrace.
> > + */
> > + if (bdev && bdev != bdev->bd_contains)
> > + p = bdev->bd_part;
> >
> > + if (p)
> > + return p->debugfs_dir;
> > +
> > + return q->debugfs_dir;
>
> This could be simplified down to:
>
> if (bdev && bdev != bdev->bd_contains)
> return bdev->bd_part->debugfs_dir;
> return q->debugfs_dir;
>
> Given that bd_part is in __blkdev_get very near bd_contains.
Ah neat.
> Also given that this patch completely rewrites blk_trace_debugfs_dir is
> there any point in the previous patch?
Still think it helps with making this patch easier to read, but I don't
care, lemme know if I should just fold it.
> > @@ -491,6 +500,7 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
> > struct dentry *dir = NULL;
> > int ret;
> >
> > +
> > if (!buts->buf_size || !buts->buf_nr)
> > return -EINVAL;
> >
>
> Spurious whitespace change.
Will nuke.
Luis
next prev parent reply other threads:[~2020-04-29 11:45 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-29 7:46 [PATCH v3 0/6] block: fix blktrace debugfs use after free Luis Chamberlain
2020-04-29 7:46 ` [PATCH v3 1/6] block: revert back to synchronous request_queue removal Luis Chamberlain
2020-04-29 11:15 ` Christoph Hellwig
2020-05-02 0:22 ` Bart Van Assche
2020-05-03 10:32 ` Matthew Wilcox
2020-05-04 16:18 ` Luis Chamberlain
2020-05-04 16:16 ` Luis Chamberlain
2020-04-29 7:46 ` [PATCH v3 2/6] block: move main block debugfs initialization to its own file Luis Chamberlain
2020-04-29 11:15 ` Christoph Hellwig
2020-04-29 7:46 ` [PATCH v3 3/6] blktrace: move blktrace debugfs creation to helper function Luis Chamberlain
2020-04-29 11:20 ` Christoph Hellwig
2020-05-02 0:25 ` Bart Van Assche
2020-04-29 7:46 ` [PATCH v3 4/6] blktrace: fix debugfs use after free Luis Chamberlain
2020-04-29 9:47 ` Greg KH
2020-04-29 11:26 ` Christoph Hellwig
2020-04-29 11:45 ` Luis Chamberlain [this message]
2020-04-29 11:50 ` Christoph Hellwig
2020-04-29 12:02 ` Luis Chamberlain
2020-04-29 12:04 ` Christoph Hellwig
2020-04-29 12:21 ` Luis Chamberlain
2020-04-29 12:57 ` Greg KH
2020-05-01 15:24 ` Luis Chamberlain
2020-05-07 11:30 ` [blktrace] d106a3fdba: BUG:kernel_NULL_pointer_dereference,address kernel test robot
2020-04-29 7:46 ` [PATCH v3 5/6] blktrace: break out of blktrace setup on concurrent calls Luis Chamberlain
2020-04-29 9:49 ` Greg KH
2020-05-01 15:06 ` Luis Chamberlain
2020-05-01 15:34 ` Christoph Hellwig
2020-05-01 15:40 ` Luis Chamberlain
2020-05-01 15:50 ` Luis Chamberlain
2020-05-01 16:51 ` Greg KH
2020-04-29 7:46 ` [PATCH v3 6/6] loop: be paranoid on exit and prevent new additions / removals Luis Chamberlain
2020-04-29 9:50 ` Greg KH
2020-05-03 9:09 ` Luis Chamberlain
2020-04-29 14:05 ` Ming Lei
2020-04-29 8:48 [PATCH v3 4/6] blktrace: fix debugfs use after free Markus Elfring
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