From: Greg Kurz <groug@kaod.org>
To: Li Qiang <liq3ea@gmail.com>
Cc: Eric Blake <eblake@redhat.com>, Li Qiang <liqiang6-s@360.cn>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 1/2] 9pfs: fix information leak in xattr read
Date: Thu, 13 Oct 2016 10:08:35 +0200 [thread overview]
Message-ID: <20161013100835.0fba59a2@bahia> (raw)
In-Reply-To: <CAKXe6SK7Hr5PGqOU--vDJhTqjnkbweFXJxNS7Zzdc5DjYdzcSg@mail.gmail.com>
On Thu, 13 Oct 2016 11:30:08 +0800
Li Qiang <liq3ea@gmail.com> wrote:
> Yes, I think the limit to apply to xattr size in 9pfs is the same as the
> Linux xattr size limit, I will try to find this limit.
>
/usr/include/linux/limits.h:#define XATTR_SIZE_MAX 65536 /* size of an extended attribute value (64k) */
> Thanks.
>
> On 2016-10-13 4:49 GMT+08:00 Eric Blake <eblake@redhat.com> wrote:
>
> > On 10/12/2016 08:23 AM, Greg Kurz wrote:
> > >
> > > But in fact, I'm afraid we have a more serious problem here... size
> > > comes from the guest and could cause g_malloc() to abort if QEMU has
> > > reached some RLIMIT... we need to call g_try_malloc0() and return
> > > ENOMEM if the allocation fails.
> >
> > Even if it does not cause an ENOMEM failure right away, the guest can
> > also use this to chew up lots of host resources. It may also be worth
> > putting a reasonable cap at the maximum the guest can allocate, rather
> > than just trying to malloc every possible size.
> >
> > --
> > Eric Blake eblake redhat com +1-919-301-3266
> > Libvirt virtualization library http://libvirt.org
> >
> >
next prev parent reply other threads:[~2016-10-13 8:08 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-09 5:25 [Qemu-devel] [PATCH 0/2] 9pfs: fix xattr issues Li Qiang
2016-10-09 5:26 ` [Qemu-devel] [PATCH 1/2] 9pfs: fix information leak in xattr read Li Qiang
2016-10-10 8:56 ` Greg Kurz
2016-10-12 13:23 ` Greg Kurz
2016-10-12 20:49 ` Eric Blake
2016-10-13 3:30 ` Li Qiang
2016-10-13 8:08 ` Greg Kurz [this message]
2016-10-13 7:51 ` Greg Kurz
2016-10-09 5:27 ` [Qemu-devel] [PATCH 2/2] 9pfs: fix memory leak about xattr value Li Qiang
2016-10-10 9:06 ` Greg Kurz
2016-10-10 9:15 ` Li Qiang
2016-10-10 10:21 ` Greg Kurz
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