From: Luis Chamberlain <mcgrof@kernel.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: axboe@kernel.dk, viro@zeniv.linux.org.uk, bvanassche@acm.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 v3 6/6] loop: be paranoid on exit and prevent new additions / removals
Date: Sun, 3 May 2020 09:09:23 +0000 [thread overview]
Message-ID: <20200503090923.GP11244@42.do-not-panic.com> (raw)
In-Reply-To: <20200429095034.GC2081185@kroah.com>
On Wed, Apr 29, 2020 at 11:50:34AM +0200, Greg KH wrote:
> On Wed, Apr 29, 2020 at 07:46:27AM +0000, Luis Chamberlain wrote:
> > Be pedantic on removal as well and hold the mutex.
> > This should prevent uses of addition while we exit.
> >
> > Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> > ---
> > drivers/block/loop.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> > index da693e6a834e..6dccba22c9b5 100644
> > --- a/drivers/block/loop.c
> > +++ b/drivers/block/loop.c
> > @@ -2333,6 +2333,8 @@ static void __exit loop_exit(void)
> >
> > range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;
> >
> > + mutex_lock(&loop_ctl_mutex);
> > +
> > idr_for_each(&loop_index_idr, &loop_exit_cb, NULL);
> > idr_destroy(&loop_index_idr);
> >
> > @@ -2340,6 +2342,8 @@ static void __exit loop_exit(void)
> > unregister_blkdev(LOOP_MAJOR, "loop");
> >
> > misc_deregister(&loop_misc);
> > +
> > + mutex_unlock(&loop_ctl_mutex);
> > }
> >
> > module_init(loop_init);
>
> What type of issue is this helping with? Can it be triggered today? if
> so, shouldn't it be backported to stable kernels?
Just code inspection. I can't trigger a userspace test script to crash
the kernel yet, but suspect a race still does exist.
Luis
next prev parent reply other threads:[~2020-05-03 9:09 UTC|newest]
Thread overview: 34+ 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
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 [this message]
2020-04-29 14:05 ` Ming Lei
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