linux-kernel - Re: [PATCH] device-dax: fix cdev leak

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Thu, 23 Feb 2017 12:27:58 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:     linux-nvdimm <linux-nvdimm@...1.01.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] device-dax: fix cdev leak

On Thu, Feb 23, 2017 at 12:20 PM, Jason Gunthorpe
<jgunthorpe@...idianresearch.com> wrote:
> On Thu, Feb 23, 2017 at 11:22:03AM -0800, Dan Williams wrote:
>> If device_add() fails, cleanup the cdev. Otherwise, we leak a kobj_map()
>> with a stale device number.
>>
>> Fixes: ba09c01d2fa8 ("dax: convert to the cdev api")
>> Cc: <stable@...r.kernel.org>
>> Cc: Logan Gunthorpe <logang@...tatee.com>
>> Reported-by: Jason Gunthorpe <jgunthorpe@...idianresearch.com>
>> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
>>  drivers/dax/dax.c |    1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
>> index ed758b74ddf0..0f8008dd0b0c 100644
>> +++ b/drivers/dax/dax.c
>> @@ -724,6 +724,7 @@ struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
>>       dev_set_name(dev, "dax%d.%d", dax_region->id, dax_dev->id);
>>       rc = device_add(dev);
>>       if (rc) {
>> +             cdev_del(&dax_dev->cdev);
>
> This probably should call into unregister_dax_dev and just skip the
> device_unregister part.
>
> Once cdev_add returns it is possible for a mmap to have been created,
> so cleanup after that point has to go through all the other
> unregister_dax_dev steps.

Ah true. I was thinking the device node is not auto-created if the
device_add() fails, but there's theoretically nothing stopping
userspace from trying to hit this race with its own self-created
device-node.