linux-kernel - Re: [PATCH v11 04/14] s390/zcrypt: driver callback to indicate resource in use

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

Message-ID: <1e6387bc-3bc0-f244-17ae-7acc88cd3f1b@linux.ibm.com>
Date:   Mon, 16 Nov 2020 11:23:38 -0500
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Halil Pasic <pasic@...ux.ibm.com>
Cc:     Harald Freudenberger <freude@...ux.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, borntraeger@...ibm.com, cohuck@...hat.com,
        mjrosato@...ux.ibm.com, alex.williamson@...hat.com,
        kwankhede@...dia.com, fiuczy@...ux.ibm.com, frankja@...ux.ibm.com,
        david@...hat.com, hca@...ux.ibm.com, gor@...ux.ibm.com
Subject: Re: [PATCH v11 04/14] s390/zcrypt: driver callback to indicate
 resource in use



On 11/13/20 7:00 PM, Halil Pasic wrote:
> On Fri, 13 Nov 2020 16:30:31 -0500
> Tony Krowiak <akrowiak@...ux.ibm.com> wrote:
>
>> We will be using the mutex_trylock() function in our sysfs
>> assignment
>> interfaces which make the call to the AP bus to check permissions (which
>> also
>> locks ap_perms). If the mutex_trylock() fails, we return from the assignment
>> function with -EBUSY. This should resolve that potential deadlock issue.
> It resolves the deadlock issue only if in_use() is also doing
> mutex_trylock(), but the if in_use doesn't take the lock it
> needs to back off (and so does it's client code) i.e. a boolean as
> return value won't do.

Makes sense. I'll change the in_use callback to return an int and use
mutex_trylock() for the vfio_ap_mdev_in_use() function. If the lock
can not be obtained, the function will return -EBUSY.

>
> Regards,
> Halil