From: Anirudh Rayabharam <mail@anirudhrb.com>
To: Stefano Garzarella <sgarzare@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Jason Wang <jasowang@redhat.com>,
syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com,
kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] vhost: handle zero regions in vhost_set_memory
Date: Tue, 22 Feb 2022 01:27:35 +0530 [thread overview]
Message-ID: <YhPur8ymuiiHirUc@anirudhrb.com> (raw)
In-Reply-To: <20220221164817.obpw477w74auxlkn@sgarzare-redhat>
On Mon, Feb 21, 2022 at 05:48:17PM +0100, Stefano Garzarella wrote:
> On Mon, Feb 21, 2022 at 12:58:51PM +0530, Anirudh Rayabharam wrote:
> > Return early when userspace sends zero regions in the VHOST_SET_MEM_TABLE
> > ioctl.
> >
> > Otherwise, this causes an erroneous entry to be added to the iotlb. This
> > entry has a range size of 0 (due to u64 overflow). This then causes
> > iotlb_access_ok() to loop indefinitely resulting in a hung thread.
> > Syzbot has reported this here:
> >
> > https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
>
> IIUC vhost_iotlb_add_range() in the for loop is never called if mem.nregions
> is 0, so I'm not sure the problem reported by syzbot is related.
>
> In any case maybe this patch is fine, but currently I think we're just
> registering an iotlb without any regions, which in theory shouldn't cause
> any problems.
Sent a new patch: https://lore.kernel.org/lkml/20220221195303.13560-1-mail@anirudhrb.com/T/#u
>
> Thanks,
> Stefano
>
> >
> > Reported-and-tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> > ---
> > drivers/vhost/vhost.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index 59edb5a1ffe2..821aba60eac2 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -1428,6 +1428,8 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
> > return -EFAULT;
> > if (mem.padding)
> > return -EOPNOTSUPP;
> > + if (mem.nregions == 0)
> > + return 0;
> > if (mem.nregions > max_mem_regions)
> > return -E2BIG;
> > newmem = kvzalloc(struct_size(newmem, regions, mem.nregions),
> > --
> > 2.35.1
> >
>
prev parent reply other threads:[~2022-02-21 19:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-21 7:28 [PATCH] vhost: handle zero regions in vhost_set_memory Anirudh Rayabharam
2022-02-21 7:56 ` Jason Wang
2022-02-21 8:11 ` Anirudh Rayabharam
2022-02-21 16:48 ` Stefano Garzarella
2022-02-21 17:59 ` Anirudh Rayabharam
2022-02-21 19:57 ` Anirudh Rayabharam [this message]
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