linux-kernel - Re: Re: [PATCH] fix memory leak on kvm_vm_ioctl_create_spapr

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]

Message-ID: <87h8wsudx8.fsf@concordia.ellerman.id.au>
Date:   Mon, 28 Aug 2017 21:31:15 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Al Viro <viro@...IV.linux.org.uk>,
        Paul Mackerras <paulus@...abs.org>
Cc:     Nixiaoming <nixiaoming@...wei.com>,
        David Hildenbrand <david@...hat.com>,
        "agraf\@suse.com" <agraf@...e.com>,
        "pbonzini\@redhat.com" <pbonzini@...hat.com>,
        "rkrcmar\@redhat.com" <rkrcmar@...hat.com>,
        "benh\@kernel.crashing.org" <benh@...nel.crashing.org>,
        "kvm-ppc\@vger.kernel.org" <kvm-ppc@...r.kernel.org>,
        "kvm\@vger.kernel.org" <kvm@...r.kernel.org>,
        "linuxppc-dev\@lists.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Re: [PATCH] fix memory leak on kvm_vm_ioctl_create_spapr_tce

Al Viro <viro@...IV.linux.org.uk> writes:

> On Mon, Aug 28, 2017 at 02:38:37PM +1000, Paul Mackerras wrote:
>> On Sun, Aug 27, 2017 at 10:02:20PM +0100, Al Viro wrote:
>> > On Wed, Aug 23, 2017 at 04:06:24PM +1000, Paul Mackerras wrote:
>> > 
>> > > It seems to me that it would be better to do the anon_inode_getfd()
>> > > call before the kvm_get_kvm() call, and go to the fail label if it
>> > > fails.
>> > 
>> > And what happens if another thread does close() on the (guessed) fd?
>> 
>> Chaos ensues, but mostly because we don't have proper mutual exclusion
>> on the modifications to the list.  I'll add a mutex_lock/unlock to
>> kvm_spapr_tce_release() and move the anon_inode_getfd() call inside
>> the mutex.
>> 
>> It looks like the other possible uses of the fd (mmap, and passing it
>> as a parameter to the KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE ioctl on a KVM
>> device fd) are safe.
>
> Frankly, it's a lot saner to have "no failure points past anon_inode_getfd()"
> policy...

Actually I thought that was a hard rule. But I don't see it documented
or mentioned anywhere so I'm not sure now why I thought that.

cheers