Re: [PATCH] vhost: validate range size before adding to iotlb

Re: [PATCH] vhost: validate range size before adding to iotlb

[Jason Wang]

On Tue, Feb 22, 2022 at 3:53 AM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
>
> In vhost_iotlb_add_range_ctx(), validate the range size is non-zero
> before proceeding with adding it to the iotlb.
>
> Range size can overflow to 0 when start is 0 and last is (2^64 - 1).
> One instance where it can happen is when userspace sends an IOTLB
> message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an
> entry with size = 0, start = 0, last = (2^64 - 1) ends up in the
> iotlb. Next time a packet is sent, iotlb_access_ok() loops
> indefinitely due to that erroneous entry:
>
>         Call Trace:
>          <TASK>
>          iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340
>          vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366
>          vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104
>          vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372
>          kthread+0x2e9/0x3a0 kernel/kthread.c:377
>          ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
>          </TASK>
>
> Reported by syzbot at:
>         https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
>
> Reported-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> Tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> ---
>  drivers/vhost/iotlb.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c
> index 670d56c879e5..b9de74bd2f9c 100644
> --- a/drivers/vhost/iotlb.c
> +++ b/drivers/vhost/iotlb.c
> @@ -53,8 +53,10 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
>                               void *opaque)
>  {
>         struct vhost_iotlb_map *map;
> +       u64 size = last - start + 1;
>
> -       if (last < start)
> +       // size can overflow to 0 when start is 0 and last is (2^64 - 1).
> +       if (last < start || size == 0)
>                 return -EFAULT;

I'd move this check to vhost_chr_iter_write(), then for the device who
has its own msg handler (e.g vDPA) can benefit from it as well.

Thanks

>
>         if (iotlb->limit &&
> @@ -69,7 +71,7 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
>                 return -ENOMEM;
>
>         map->start = start;
> -       map->size = last - start + 1;
> +       map->size = size;
>         map->last = last;
>         map->addr = addr;
>         map->perm = perm;
> --
> 2.35.1
>

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Re: [PATCH] vhost: validate range size before adding to iotlb

[Jason Wang]

On Tue, Feb 22, 2022 at 12:57 PM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
>
> On Tue, Feb 22, 2022 at 10:50:20AM +0800, Jason Wang wrote:
> > On Tue, Feb 22, 2022 at 3:53 AM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> > >
> > > In vhost_iotlb_add_range_ctx(), validate the range size is non-zero
> > > before proceeding with adding it to the iotlb.
> > >
> > > Range size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > One instance where it can happen is when userspace sends an IOTLB
> > > message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an
> > > entry with size = 0, start = 0, last = (2^64 - 1) ends up in the
> > > iotlb. Next time a packet is sent, iotlb_access_ok() loops
> > > indefinitely due to that erroneous entry:
> > >
> > >         Call Trace:
> > >          <TASK>
> > >          iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340
> > >          vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366
> > >          vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104
> > >          vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372
> > >          kthread+0x2e9/0x3a0 kernel/kthread.c:377
> > >          ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> > >          </TASK>
> > >
> > > Reported by syzbot at:
> > >         https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
> > >
> > > Reported-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > Tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> > > ---
> > >  drivers/vhost/iotlb.c | 6 ++++--
> > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c
> > > index 670d56c879e5..b9de74bd2f9c 100644
> > > --- a/drivers/vhost/iotlb.c
> > > +++ b/drivers/vhost/iotlb.c
> > > @@ -53,8 +53,10 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > >                               void *opaque)
> > >  {
> > >         struct vhost_iotlb_map *map;
> > > +       u64 size = last - start + 1;
> > >
> > > -       if (last < start)
> > > +       // size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > +       if (last < start || size == 0)
> > >                 return -EFAULT;
> >
> > I'd move this check to vhost_chr_iter_write(), then for the device who
> > has its own msg handler (e.g vDPA) can benefit from it as well.
>
> Thanks for reviewing!
>
> I kept the check here thinking that all devices would benefit from it
> because they would need to call vhost_iotlb_add_range() to add an entry
> to the iotlb. Isn't that correct?

Correct for now but not for the future, it's not guaranteed that the
per device iotlb message handler will use vhost iotlb.

But I agree that we probably don't need to care about it too much now.

> Do you see any other benefit in moving
> it to vhost_chr_iter_write()?
>
> One concern I have is that if we move it out some future caller to
> vhost_iotlb_add_range() might forget to handle this case.

Yes.

Rethink the whole fix, we're basically rejecting [0, ULONG_MAX] range
which seems a little bit odd. I wonder if it's better to just remove
the map->size. Having a quick glance at the the user, I don't see any
blocker for this.

Thanks

>
> Thanks!
>
>         - Anirudh.
>
> >
> > Thanks
> >
> > >
> > >         if (iotlb->limit &&
> > > @@ -69,7 +71,7 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > >                 return -ENOMEM;
> > >
> > >         map->start = start;
> > > -       map->size = last - start + 1;
> > > +       map->size = size;
> > >         map->last = last;
> > >         map->addr = addr;
> > >         map->perm = perm;
> > > --
> > > 2.35.1
> > >
> >
>

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Re: [PATCH] vhost: validate range size before adding to iotlb

[Michael S. Tsirkin]

On Tue, Feb 22, 2022 at 03:11:07PM +0800, Jason Wang wrote:
> On Tue, Feb 22, 2022 at 12:57 PM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> >
> > On Tue, Feb 22, 2022 at 10:50:20AM +0800, Jason Wang wrote:
> > > On Tue, Feb 22, 2022 at 3:53 AM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> > > >
> > > > In vhost_iotlb_add_range_ctx(), validate the range size is non-zero
> > > > before proceeding with adding it to the iotlb.
> > > >
> > > > Range size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > > One instance where it can happen is when userspace sends an IOTLB
> > > > message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an
> > > > entry with size = 0, start = 0, last = (2^64 - 1) ends up in the
> > > > iotlb. Next time a packet is sent, iotlb_access_ok() loops
> > > > indefinitely due to that erroneous entry:
> > > >
> > > >         Call Trace:
> > > >          <TASK>
> > > >          iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340
> > > >          vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366
> > > >          vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104
> > > >          vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372
> > > >          kthread+0x2e9/0x3a0 kernel/kthread.c:377
> > > >          ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> > > >          </TASK>
> > > >
> > > > Reported by syzbot at:
> > > >         https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
> > > >
> > > > Reported-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > > Tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> > > > ---
> > > >  drivers/vhost/iotlb.c | 6 ++++--
> > > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c
> > > > index 670d56c879e5..b9de74bd2f9c 100644
> > > > --- a/drivers/vhost/iotlb.c
> > > > +++ b/drivers/vhost/iotlb.c
> > > > @@ -53,8 +53,10 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > > >                               void *opaque)
> > > >  {
> > > >         struct vhost_iotlb_map *map;
> > > > +       u64 size = last - start + 1;
> > > >
> > > > -       if (last < start)
> > > > +       // size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > > +       if (last < start || size == 0)
> > > >                 return -EFAULT;
> > >
> > > I'd move this check to vhost_chr_iter_write(), then for the device who
> > > has its own msg handler (e.g vDPA) can benefit from it as well.
> >
> > Thanks for reviewing!
> >
> > I kept the check here thinking that all devices would benefit from it
> > because they would need to call vhost_iotlb_add_range() to add an entry
> > to the iotlb. Isn't that correct?
> 
> Correct for now but not for the future, it's not guaranteed that the
> per device iotlb message handler will use vhost iotlb.
> 
> But I agree that we probably don't need to care about it too much now.
> 
> > Do you see any other benefit in moving
> > it to vhost_chr_iter_write()?
> >
> > One concern I have is that if we move it out some future caller to
> > vhost_iotlb_add_range() might forget to handle this case.
> 
> Yes.
> 
> Rethink the whole fix, we're basically rejecting [0, ULONG_MAX] range
> which seems a little bit odd.

Well, I guess ideally we'd split this up as two entries - this kind of
thing is after all one of the reasons we initially used first,last as
the API - as opposed to first,size.

Anirudh, could you do it like this instead of rejecting?


> I wonder if it's better to just remove
> the map->size. Having a quick glance at the the user, I don't see any
> blocker for this.
> 
> Thanks

I think it's possible but won't solve the bug by itself, and we'd need
to review and fix all users - a high chance of introducing
another regression. And I think there's value of fitting under the
stable rule of 100 lines with context.
So sure, but let's fix the bug first.



> >
> > Thanks!
> >
> >         - Anirudh.
> >
> > >
> > > Thanks
> > >
> > > >
> > > >         if (iotlb->limit &&
> > > > @@ -69,7 +71,7 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > > >                 return -ENOMEM;
> > > >
> > > >         map->start = start;
> > > > -       map->size = last - start + 1;
> > > > +       map->size = size;
> > > >         map->last = last;
> > > >         map->addr = addr;
> > > >         map->perm = perm;
> > > > --
> > > > 2.35.1
> > > >
> > >
> >

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Re: [PATCH] vhost: validate range size before adding to iotlb

[Michael S. Tsirkin]

On Tue, Feb 22, 2022 at 10:57:41PM +0530, Anirudh Rayabharam wrote:
> On Tue, Feb 22, 2022 at 10:02:29AM -0500, Michael S. Tsirkin wrote:
> > On Tue, Feb 22, 2022 at 03:11:07PM +0800, Jason Wang wrote:
> > > On Tue, Feb 22, 2022 at 12:57 PM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> > > >
> > > > On Tue, Feb 22, 2022 at 10:50:20AM +0800, Jason Wang wrote:
> > > > > On Tue, Feb 22, 2022 at 3:53 AM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> > > > > >
> > > > > > In vhost_iotlb_add_range_ctx(), validate the range size is non-zero
> > > > > > before proceeding with adding it to the iotlb.
> > > > > >
> > > > > > Range size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > > > > One instance where it can happen is when userspace sends an IOTLB
> > > > > > message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an
> > > > > > entry with size = 0, start = 0, last = (2^64 - 1) ends up in the
> > > > > > iotlb. Next time a packet is sent, iotlb_access_ok() loops
> > > > > > indefinitely due to that erroneous entry:
> > > > > >
> > > > > >         Call Trace:
> > > > > >          <TASK>
> > > > > >          iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340
> > > > > >          vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366
> > > > > >          vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104
> > > > > >          vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372
> > > > > >          kthread+0x2e9/0x3a0 kernel/kthread.c:377
> > > > > >          ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> > > > > >          </TASK>
> > > > > >
> > > > > > Reported by syzbot at:
> > > > > >         https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
> > > > > >
> > > > > > Reported-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > > > > Tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > > > > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> > > > > > ---
> > > > > >  drivers/vhost/iotlb.c | 6 ++++--
> > > > > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c
> > > > > > index 670d56c879e5..b9de74bd2f9c 100644
> > > > > > --- a/drivers/vhost/iotlb.c
> > > > > > +++ b/drivers/vhost/iotlb.c
> > > > > > @@ -53,8 +53,10 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > > > > >                               void *opaque)
> > > > > >  {
> > > > > >         struct vhost_iotlb_map *map;
> > > > > > +       u64 size = last - start + 1;
> > > > > >
> > > > > > -       if (last < start)
> > > > > > +       // size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > > > > +       if (last < start || size == 0)
> > > > > >                 return -EFAULT;
> > > > >
> > > > > I'd move this check to vhost_chr_iter_write(), then for the device who
> > > > > has its own msg handler (e.g vDPA) can benefit from it as well.
> > > >
> > > > Thanks for reviewing!
> > > >
> > > > I kept the check here thinking that all devices would benefit from it
> > > > because they would need to call vhost_iotlb_add_range() to add an entry
> > > > to the iotlb. Isn't that correct?
> > > 
> > > Correct for now but not for the future, it's not guaranteed that the
> > > per device iotlb message handler will use vhost iotlb.
> > > 
> > > But I agree that we probably don't need to care about it too much now.
> > > 
> > > > Do you see any other benefit in moving
> > > > it to vhost_chr_iter_write()?
> > > >
> > > > One concern I have is that if we move it out some future caller to
> > > > vhost_iotlb_add_range() might forget to handle this case.
> > > 
> > > Yes.
> > > 
> > > Rethink the whole fix, we're basically rejecting [0, ULONG_MAX] range
> > > which seems a little bit odd.
> > 
> > Well, I guess ideally we'd split this up as two entries - this kind of
> > thing is after all one of the reasons we initially used first,last as
> > the API - as opposed to first,size.
> 
> IIUC, the APIs exposed to userspace accept first,size.

Some of them.


/* vhost vdpa IOVA range
 * @first: First address that can be mapped by vhost-vDPA
 * @last: Last address that can be mapped by vhost-vDPA
 */
struct vhost_vdpa_iova_range {
        __u64 first;
        __u64 last;
};

but

struct vhost_iotlb_msg {
        __u64 iova;
        __u64 size;
        __u64 uaddr;
#define VHOST_ACCESS_RO      0x1
#define VHOST_ACCESS_WO      0x2
#define VHOST_ACCESS_RW      0x3
        __u8 perm;
#define VHOST_IOTLB_MISS           1
#define VHOST_IOTLB_UPDATE         2
#define VHOST_IOTLB_INVALIDATE     3
#define VHOST_IOTLB_ACCESS_FAIL    4
/*
 * VHOST_IOTLB_BATCH_BEGIN and VHOST_IOTLB_BATCH_END allow modifying
 * multiple mappings in one go: beginning with
 * VHOST_IOTLB_BATCH_BEGIN, followed by any number of
 * VHOST_IOTLB_UPDATE messages, and ending with VHOST_IOTLB_BATCH_END.
 * When one of these two values is used as the message type, the rest
 * of the fields in the message are ignored. There's no guarantee that
 * these changes take place automatically in the device.
 */
#define VHOST_IOTLB_BATCH_BEGIN    5
#define VHOST_IOTLB_BATCH_END      6
        __u8 type;
};



> Which means that
> right now there is now way for userspace to map this range. So, is there
> any value in not simply rejecting this range?
> 
> > 
> > Anirudh, could you do it like this instead of rejecting?
> > 
> > 
> > > I wonder if it's better to just remove
> > > the map->size. Having a quick glance at the the user, I don't see any
> > > blocker for this.
> > > 
> > > Thanks
> > 
> > I think it's possible but won't solve the bug by itself, and we'd need
> > to review and fix all users - a high chance of introducing
> > another regression. 
> 
> Agreed, I did a quick review of the usages and getting rid of size
> didn't seem trivial.
> 
> Thanks,
> 
> 	- Anirudh.
> 
> > And I think there's value of fitting under the
> > stable rule of 100 lines with context.
> > So sure, but let's fix the bug first.
> > 
> > 
> > 
> > > >
> > > > Thanks!
> > > >
> > > >         - Anirudh.
> > > >
> > > > >
> > > > > Thanks
> > > > >
> > > > > >
> > > > > >         if (iotlb->limit &&
> > > > > > @@ -69,7 +71,7 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > > > > >                 return -ENOMEM;
> > > > > >
> > > > > >         map->start = start;
> > > > > > -       map->size = last - start + 1;
> > > > > > +       map->size = size;
> > > > > >         map->last = last;
> > > > > >         map->addr = addr;
> > > > > >         map->perm = perm;
> > > > > > --
> > > > > > 2.35.1
> > > > > >
> > > > >
> > > >
> > 

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Re: [PATCH] vhost: validate range size before adding to iotlb

[Michael S. Tsirkin]

On Wed, Feb 23, 2022 at 07:48:18PM +0530, Anirudh Rayabharam wrote:
> On Tue, Feb 22, 2022 at 06:21:50PM -0500, Michael S. Tsirkin wrote:
> > On Tue, Feb 22, 2022 at 10:57:41PM +0530, Anirudh Rayabharam wrote:
> > > On Tue, Feb 22, 2022 at 10:02:29AM -0500, Michael S. Tsirkin wrote:
> > > > On Tue, Feb 22, 2022 at 03:11:07PM +0800, Jason Wang wrote:
> > > > > On Tue, Feb 22, 2022 at 12:57 PM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> > > > > >
> > > > > > On Tue, Feb 22, 2022 at 10:50:20AM +0800, Jason Wang wrote:
> > > > > > > On Tue, Feb 22, 2022 at 3:53 AM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> > > > > > > >
> > > > > > > > In vhost_iotlb_add_range_ctx(), validate the range size is non-zero
> > > > > > > > before proceeding with adding it to the iotlb.
> > > > > > > >
> > > > > > > > Range size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > > > > > > One instance where it can happen is when userspace sends an IOTLB
> > > > > > > > message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an
> > > > > > > > entry with size = 0, start = 0, last = (2^64 - 1) ends up in the
> > > > > > > > iotlb. Next time a packet is sent, iotlb_access_ok() loops
> > > > > > > > indefinitely due to that erroneous entry:
> > > > > > > >
> > > > > > > >         Call Trace:
> > > > > > > >          <TASK>
> > > > > > > >          iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340
> > > > > > > >          vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366
> > > > > > > >          vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104
> > > > > > > >          vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372
> > > > > > > >          kthread+0x2e9/0x3a0 kernel/kthread.c:377
> > > > > > > >          ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> > > > > > > >          </TASK>
> > > > > > > >
> > > > > > > > Reported by syzbot at:
> > > > > > > >         https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
> > > > > > > >
> > > > > > > > Reported-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > > > > > > Tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > > > > > > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> > > > > > > > ---
> > > > > > > >  drivers/vhost/iotlb.c | 6 ++++--
> > > > > > > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c
> > > > > > > > index 670d56c879e5..b9de74bd2f9c 100644
> > > > > > > > --- a/drivers/vhost/iotlb.c
> > > > > > > > +++ b/drivers/vhost/iotlb.c
> > > > > > > > @@ -53,8 +53,10 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > > > > > > >                               void *opaque)
> > > > > > > >  {
> > > > > > > >         struct vhost_iotlb_map *map;
> > > > > > > > +       u64 size = last - start + 1;
> > > > > > > >
> > > > > > > > -       if (last < start)
> > > > > > > > +       // size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > > > > > > +       if (last < start || size == 0)
> > > > > > > >                 return -EFAULT;
> > > > > > >
> > > > > > > I'd move this check to vhost_chr_iter_write(), then for the device who
> > > > > > > has its own msg handler (e.g vDPA) can benefit from it as well.
> > > > > >
> > > > > > Thanks for reviewing!
> > > > > >
> > > > > > I kept the check here thinking that all devices would benefit from it
> > > > > > because they would need to call vhost_iotlb_add_range() to add an entry
> > > > > > to the iotlb. Isn't that correct?
> > > > > 
> > > > > Correct for now but not for the future, it's not guaranteed that the
> > > > > per device iotlb message handler will use vhost iotlb.
> > > > > 
> > > > > But I agree that we probably don't need to care about it too much now.
> > > > > 
> > > > > > Do you see any other benefit in moving
> > > > > > it to vhost_chr_iter_write()?
> > > > > >
> > > > > > One concern I have is that if we move it out some future caller to
> > > > > > vhost_iotlb_add_range() might forget to handle this case.
> > > > > 
> > > > > Yes.
> > > > > 
> > > > > Rethink the whole fix, we're basically rejecting [0, ULONG_MAX] range
> > > > > which seems a little bit odd.
> > > > 
> > > > Well, I guess ideally we'd split this up as two entries - this kind of
> > > > thing is after all one of the reasons we initially used first,last as
> > > > the API - as opposed to first,size.
> > > 
> > > IIUC, the APIs exposed to userspace accept first,size.
> > 
> > Some of them.
> > 
> > 
> > /* vhost vdpa IOVA range
> >  * @first: First address that can be mapped by vhost-vDPA
> >  * @last: Last address that can be mapped by vhost-vDPA
> >  */
> > struct vhost_vdpa_iova_range {
> >         __u64 first;
> >         __u64 last;
> > };
> 
> Alright, I will split it into two entries. That doesn't fully address
> the bug though. I would also need to validate size in vhost_chr_iter_write().

Do you mean vhost_chr_write_iter?

> 
> Should I do both in one patch or as a two patch series?

I'm not sure why we need to do validation in vhost_chr_iter_write,
hard to say without seeing the patch.

> > 
> > but
> > 
> > struct vhost_iotlb_msg {
> >         __u64 iova;
> >         __u64 size;
> >         __u64 uaddr;
> > #define VHOST_ACCESS_RO      0x1
> > #define VHOST_ACCESS_WO      0x2
> > #define VHOST_ACCESS_RW      0x3
> >         __u8 perm;
> > #define VHOST_IOTLB_MISS           1
> > #define VHOST_IOTLB_UPDATE         2
> > #define VHOST_IOTLB_INVALIDATE     3
> > #define VHOST_IOTLB_ACCESS_FAIL    4
> > /*
> >  * VHOST_IOTLB_BATCH_BEGIN and VHOST_IOTLB_BATCH_END allow modifying
> >  * multiple mappings in one go: beginning with
> >  * VHOST_IOTLB_BATCH_BEGIN, followed by any number of
> >  * VHOST_IOTLB_UPDATE messages, and ending with VHOST_IOTLB_BATCH_END.
> >  * When one of these two values is used as the message type, the rest
> >  * of the fields in the message are ignored. There's no guarantee that
> >  * these changes take place automatically in the device.
> >  */
> > #define VHOST_IOTLB_BATCH_BEGIN    5
> > #define VHOST_IOTLB_BATCH_END      6
> >         __u8 type;
> > };
> > 
> > 
> > 
> > > Which means that
> > > right now there is now way for userspace to map this range. So, is there
> > > any value in not simply rejecting this range?
> > > 
> > > > 
> > > > Anirudh, could you do it like this instead of rejecting?
> > > > 
> > > > 
> > > > > I wonder if it's better to just remove
> > > > > the map->size. Having a quick glance at the the user, I don't see any
> > > > > blocker for this.
> > > > > 
> > > > > Thanks
> > > > 
> > > > I think it's possible but won't solve the bug by itself, and we'd need
> > > > to review and fix all users - a high chance of introducing
> > > > another regression. 
> > > 
> > > Agreed, I did a quick review of the usages and getting rid of size
> > > didn't seem trivial.
> > > 
> > > Thanks,
> > > 
> > > 	- Anirudh.
> > > 
> > > > And I think there's value of fitting under the
> > > > stable rule of 100 lines with context.
> > > > So sure, but let's fix the bug first.
> > > > 
> > > > 
> > > > 
> > > > > >
> > > > > > Thanks!
> > > > > >
> > > > > >         - Anirudh.
> > > > > >
> > > > > > >
> > > > > > > Thanks
> > > > > > >
> > > > > > > >
> > > > > > > >         if (iotlb->limit &&
> > > > > > > > @@ -69,7 +71,7 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > > > > > > >                 return -ENOMEM;
> > > > > > > >
> > > > > > > >         map->start = start;
> > > > > > > > -       map->size = last - start + 1;
> > > > > > > > +       map->size = size;
> > > > > > > >         map->last = last;
> > > > > > > >         map->addr = addr;
> > > > > > > >         map->perm = perm;
> > > > > > > > --
> > > > > > > > 2.35.1
> > > > > > > >
> > > > > > >
> > > > > >
> > > > 
> > 

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Virtualization@lists.linux-foundation.org
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Re: [PATCH] vhost: validate range size before adding to iotlb

[Michael S. Tsirkin]

On Wed, Feb 23, 2022 at 10:19:23PM +0530, Anirudh Rayabharam wrote:
> On Wed, Feb 23, 2022 at 10:15:01AM -0500, Michael S. Tsirkin wrote:
> > On Wed, Feb 23, 2022 at 07:48:18PM +0530, Anirudh Rayabharam wrote:
> > > On Tue, Feb 22, 2022 at 06:21:50PM -0500, Michael S. Tsirkin wrote:
> > > > On Tue, Feb 22, 2022 at 10:57:41PM +0530, Anirudh Rayabharam wrote:
> > > > > On Tue, Feb 22, 2022 at 10:02:29AM -0500, Michael S. Tsirkin wrote:
> > > > > > On Tue, Feb 22, 2022 at 03:11:07PM +0800, Jason Wang wrote:
> > > > > > > On Tue, Feb 22, 2022 at 12:57 PM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> > > > > > > >
> > > > > > > > On Tue, Feb 22, 2022 at 10:50:20AM +0800, Jason Wang wrote:
> > > > > > > > > On Tue, Feb 22, 2022 at 3:53 AM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> > > > > > > > > >
> > > > > > > > > > In vhost_iotlb_add_range_ctx(), validate the range size is non-zero
> > > > > > > > > > before proceeding with adding it to the iotlb.
> > > > > > > > > >
> > > > > > > > > > Range size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > > > > > > > > One instance where it can happen is when userspace sends an IOTLB
> > > > > > > > > > message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an
> > > > > > > > > > entry with size = 0, start = 0, last = (2^64 - 1) ends up in the
> > > > > > > > > > iotlb. Next time a packet is sent, iotlb_access_ok() loops
> > > > > > > > > > indefinitely due to that erroneous entry:
> > > > > > > > > >
> > > > > > > > > >         Call Trace:
> > > > > > > > > >          <TASK>
> > > > > > > > > >          iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340
> > > > > > > > > >          vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366
> > > > > > > > > >          vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104
> > > > > > > > > >          vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372
> > > > > > > > > >          kthread+0x2e9/0x3a0 kernel/kthread.c:377
> > > > > > > > > >          ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> > > > > > > > > >          </TASK>
> > > > > > > > > >
> > > > > > > > > > Reported by syzbot at:
> > > > > > > > > >         https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
> > > > > > > > > >
> > > > > > > > > > Reported-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > > > > > > > > Tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > > > > > > > > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> > > > > > > > > > ---
> > > > > > > > > >  drivers/vhost/iotlb.c | 6 ++++--
> > > > > > > > > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > > > > > > > > >
> > > > > > > > > > diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c
> > > > > > > > > > index 670d56c879e5..b9de74bd2f9c 100644
> > > > > > > > > > --- a/drivers/vhost/iotlb.c
> > > > > > > > > > +++ b/drivers/vhost/iotlb.c
> > > > > > > > > > @@ -53,8 +53,10 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > > > > > > > > >                               void *opaque)
> > > > > > > > > >  {
> > > > > > > > > >         struct vhost_iotlb_map *map;
> > > > > > > > > > +       u64 size = last - start + 1;
> > > > > > > > > >
> > > > > > > > > > -       if (last < start)
> > > > > > > > > > +       // size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > > > > > > > > +       if (last < start || size == 0)
> > > > > > > > > >                 return -EFAULT;
> > > > > > > > >
> > > > > > > > > I'd move this check to vhost_chr_iter_write(), then for the device who
> > > > > > > > > has its own msg handler (e.g vDPA) can benefit from it as well.
> > > > > > > >
> > > > > > > > Thanks for reviewing!
> > > > > > > >
> > > > > > > > I kept the check here thinking that all devices would benefit from it
> > > > > > > > because they would need to call vhost_iotlb_add_range() to add an entry
> > > > > > > > to the iotlb. Isn't that correct?
> > > > > > > 
> > > > > > > Correct for now but not for the future, it's not guaranteed that the
> > > > > > > per device iotlb message handler will use vhost iotlb.
> > > > > > > 
> > > > > > > But I agree that we probably don't need to care about it too much now.
> > > > > > > 
> > > > > > > > Do you see any other benefit in moving
> > > > > > > > it to vhost_chr_iter_write()?
> > > > > > > >
> > > > > > > > One concern I have is that if we move it out some future caller to
> > > > > > > > vhost_iotlb_add_range() might forget to handle this case.
> > > > > > > 
> > > > > > > Yes.
> > > > > > > 
> > > > > > > Rethink the whole fix, we're basically rejecting [0, ULONG_MAX] range
> > > > > > > which seems a little bit odd.
> > > > > > 
> > > > > > Well, I guess ideally we'd split this up as two entries - this kind of
> > > > > > thing is after all one of the reasons we initially used first,last as
> > > > > > the API - as opposed to first,size.
> > > > > 
> > > > > IIUC, the APIs exposed to userspace accept first,size.
> > > > 
> > > > Some of them.
> > > > 
> > > > 
> > > > /* vhost vdpa IOVA range
> > > >  * @first: First address that can be mapped by vhost-vDPA
> > > >  * @last: Last address that can be mapped by vhost-vDPA
> > > >  */
> > > > struct vhost_vdpa_iova_range {
> > > >         __u64 first;
> > > >         __u64 last;
> > > > };
> > > 
> > > Alright, I will split it into two entries. That doesn't fully address
> > > the bug though. I would also need to validate size in vhost_chr_iter_write().
> > 
> > Do you mean vhost_chr_write_iter?
> 
> Yes, my bad.
> 
> > 
> > > 
> > > Should I do both in one patch or as a two patch series?
> > 
> > I'm not sure why we need to do validation in vhost_chr_iter_write,
> > hard to say without seeing the patch.
> 
> Well, if userspace sends iova = 0 and size = 0 in vhost_iotlb_msg, we will end
> up mapping the range [0, ULONG_MAX] in iotlb which doesn't make sense. We
> should probably reject when size = 0.
> 
> As Jason pointed out [1], having the check in vhost_chr_write_iter() will
> also benefit devices that have their own message handler.
> 
> [1]: https://lore.kernel.org/kvm/CACGkMEvLE=kV4PxJLRjdSyKArU+MRx6b_mbLGZHSUgoAAZ+-Fg@mail.gmail.com/

Oh. Makes sense.

I think one patch is enough.

> > 
> > > > 
> > > > but
> > > > 
> > > > struct vhost_iotlb_msg {
> > > >         __u64 iova;
> > > >         __u64 size;
> > > >         __u64 uaddr;
> > > > #define VHOST_ACCESS_RO      0x1
> > > > #define VHOST_ACCESS_WO      0x2
> > > > #define VHOST_ACCESS_RW      0x3
> > > >         __u8 perm;
> > > > #define VHOST_IOTLB_MISS           1
> > > > #define VHOST_IOTLB_UPDATE         2
> > > > #define VHOST_IOTLB_INVALIDATE     3
> > > > #define VHOST_IOTLB_ACCESS_FAIL    4
> > > > /*
> > > >  * VHOST_IOTLB_BATCH_BEGIN and VHOST_IOTLB_BATCH_END allow modifying
> > > >  * multiple mappings in one go: beginning with
> > > >  * VHOST_IOTLB_BATCH_BEGIN, followed by any number of
> > > >  * VHOST_IOTLB_UPDATE messages, and ending with VHOST_IOTLB_BATCH_END.
> > > >  * When one of these two values is used as the message type, the rest
> > > >  * of the fields in the message are ignored. There's no guarantee that
> > > >  * these changes take place automatically in the device.
> > > >  */
> > > > #define VHOST_IOTLB_BATCH_BEGIN    5
> > > > #define VHOST_IOTLB_BATCH_END      6
> > > >         __u8 type;
> > > > };
> > > > 
> > > > 
> > > > 
> > > > > Which means that
> > > > > right now there is now way for userspace to map this range. So, is there
> > > > > any value in not simply rejecting this range?
> > > > > 
> > > > > > 
> > > > > > Anirudh, could you do it like this instead of rejecting?
> > > > > > 
> > > > > > 
> > > > > > > I wonder if it's better to just remove
> > > > > > > the map->size. Having a quick glance at the the user, I don't see any
> > > > > > > blocker for this.
> > > > > > > 
> > > > > > > Thanks
> > > > > > 
> > > > > > I think it's possible but won't solve the bug by itself, and we'd need
> > > > > > to review and fix all users - a high chance of introducing
> > > > > > another regression. 
> > > > > 
> > > > > Agreed, I did a quick review of the usages and getting rid of size
> > > > > didn't seem trivial.
> > > > > 
> > > > > Thanks,
> > > > > 
> > > > > 	- Anirudh.
> > > > > 
> > > > > > And I think there's value of fitting under the
> > > > > > stable rule of 100 lines with context.
> > > > > > So sure, but let's fix the bug first.
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > > >
> > > > > > > > Thanks!
> > > > > > > >
> > > > > > > >         - Anirudh.
> > > > > > > >
> > > > > > > > >
> > > > > > > > > Thanks
> > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >         if (iotlb->limit &&
> > > > > > > > > > @@ -69,7 +71,7 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > > > > > > > > >                 return -ENOMEM;
> > > > > > > > > >
> > > > > > > > > >         map->start = start;
> > > > > > > > > > -       map->size = last - start + 1;
> > > > > > > > > > +       map->size = size;
> > > > > > > > > >         map->last = last;
> > > > > > > > > >         map->addr = addr;
> > > > > > > > > >         map->perm = perm;
> > > > > > > > > > --
> > > > > > > > > > 2.35.1
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > 
> > > > 
> > 

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Re: [PATCH] vhost: validate range size before adding to iotlb

[Jason Wang]

On Tue, Feb 22, 2022 at 11:02 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Tue, Feb 22, 2022 at 03:11:07PM +0800, Jason Wang wrote:
> > On Tue, Feb 22, 2022 at 12:57 PM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> > >
> > > On Tue, Feb 22, 2022 at 10:50:20AM +0800, Jason Wang wrote:
> > > > On Tue, Feb 22, 2022 at 3:53 AM Anirudh Rayabharam <mail@anirudhrb.com> wrote:
> > > > >
> > > > > In vhost_iotlb_add_range_ctx(), validate the range size is non-zero
> > > > > before proceeding with adding it to the iotlb.
> > > > >
> > > > > Range size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > > > One instance where it can happen is when userspace sends an IOTLB
> > > > > message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an
> > > > > entry with size = 0, start = 0, last = (2^64 - 1) ends up in the
> > > > > iotlb. Next time a packet is sent, iotlb_access_ok() loops
> > > > > indefinitely due to that erroneous entry:
> > > > >
> > > > >         Call Trace:
> > > > >          <TASK>
> > > > >          iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340
> > > > >          vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366
> > > > >          vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104
> > > > >          vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372
> > > > >          kthread+0x2e9/0x3a0 kernel/kthread.c:377
> > > > >          ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> > > > >          </TASK>
> > > > >
> > > > > Reported by syzbot at:
> > > > >         https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
> > > > >
> > > > > Reported-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > > > Tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> > > > > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> > > > > ---
> > > > >  drivers/vhost/iotlb.c | 6 ++++--
> > > > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c
> > > > > index 670d56c879e5..b9de74bd2f9c 100644
> > > > > --- a/drivers/vhost/iotlb.c
> > > > > +++ b/drivers/vhost/iotlb.c
> > > > > @@ -53,8 +53,10 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > > > >                               void *opaque)
> > > > >  {
> > > > >         struct vhost_iotlb_map *map;
> > > > > +       u64 size = last - start + 1;
> > > > >
> > > > > -       if (last < start)
> > > > > +       // size can overflow to 0 when start is 0 and last is (2^64 - 1).
> > > > > +       if (last < start || size == 0)
> > > > >                 return -EFAULT;
> > > >
> > > > I'd move this check to vhost_chr_iter_write(), then for the device who
> > > > has its own msg handler (e.g vDPA) can benefit from it as well.
> > >
> > > Thanks for reviewing!
> > >
> > > I kept the check here thinking that all devices would benefit from it
> > > because they would need to call vhost_iotlb_add_range() to add an entry
> > > to the iotlb. Isn't that correct?
> >
> > Correct for now but not for the future, it's not guaranteed that the
> > per device iotlb message handler will use vhost iotlb.
> >
> > But I agree that we probably don't need to care about it too much now.
> >
> > > Do you see any other benefit in moving
> > > it to vhost_chr_iter_write()?
> > >
> > > One concern I have is that if we move it out some future caller to
> > > vhost_iotlb_add_range() might forget to handle this case.
> >
> > Yes.
> >
> > Rethink the whole fix, we're basically rejecting [0, ULONG_MAX] range
> > which seems a little bit odd.
>
> Well, I guess ideally we'd split this up as two entries - this kind of
> thing is after all one of the reasons we initially used first,last as
> the API - as opposed to first,size.
>
> Anirudh, could you do it like this instead of rejecting?
>
>
> > I wonder if it's better to just remove
> > the map->size. Having a quick glance at the the user, I don't see any
> > blocker for this.
> >
> > Thanks
>
> I think it's possible but won't solve the bug by itself, and we'd need
> to review and fix all users - a high chance of introducing
> another regression. And I think there's value of fitting under the
> stable rule of 100 lines with context.
> So sure, but let's fix the bug first.

Ok, I agree.

Thanks

>
>
>
> > >
> > > Thanks!
> > >
> > >         - Anirudh.
> > >
> > > >
> > > > Thanks
> > > >
> > > > >
> > > > >         if (iotlb->limit &&
> > > > > @@ -69,7 +71,7 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
> > > > >                 return -ENOMEM;
> > > > >
> > > > >         map->start = start;
> > > > > -       map->size = last - start + 1;
> > > > > +       map->size = size;
> > > > >         map->last = last;
> > > > >         map->addr = addr;
> > > > >         map->perm = perm;
> > > > > --
> > > > > 2.35.1
> > > > >
> > > >
> > >
>

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Re: [PATCH] vhost: validate range size before adding to iotlb

[Michael S. Tsirkin]

On Tue, Feb 22, 2022 at 01:23:03AM +0530, Anirudh Rayabharam wrote:
> In vhost_iotlb_add_range_ctx(), validate the range size is non-zero
> before proceeding with adding it to the iotlb.
> 
> Range size can overflow to 0 when start is 0 and last is (2^64 - 1).
> One instance where it can happen is when userspace sends an IOTLB
> message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an
> entry with size = 0, start = 0, last = (2^64 - 1) ends up in the
> iotlb. Next time a packet is sent, iotlb_access_ok() loops
> indefinitely due to that erroneous entry:
> 
> 	Call Trace:
> 	 <TASK>
> 	 iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340
> 	 vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366
> 	 vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104
> 	 vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372
> 	 kthread+0x2e9/0x3a0 kernel/kthread.c:377
> 	 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> 	 </TASK>
> 
> Reported by syzbot at:
> 	https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
> 
> Reported-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> Tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com
> Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> ---
>  drivers/vhost/iotlb.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c
> index 670d56c879e5..b9de74bd2f9c 100644
> --- a/drivers/vhost/iotlb.c
> +++ b/drivers/vhost/iotlb.c
> @@ -53,8 +53,10 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
>  			      void *opaque)
>  {
>  	struct vhost_iotlb_map *map;
> +	u64 size = last - start + 1;
>  
> -	if (last < start)
> +	// size can overflow to 0 when start is 0 and last is (2^64 - 1).

Pls use the old-style /* */  comments.

> +	if (last < start || size == 0)
>  		return -EFAULT;
>  
>  	if (iotlb->limit &&
> @@ -69,7 +71,7 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
>  		return -ENOMEM;
>  
>  	map->start = start;
> -	map->size = last - start + 1;
> +	map->size = size;
>  	map->last = last;
>  	map->addr = addr;
>  	map->perm = perm;
> -- 
> 2.35.1

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