[PATCH v1] libvhost-user: fix VHOST_USER_REM_MEM_REG skipping mmap_addr

[PATCH v1] libvhost-user: fix VHOST_USER_REM_MEM_REG skipping mmap_addr

[David Hildenbrand]

We end up not copying the mmap_addr of all existing regions, resulting
in a SEGFAULT once we actually try to map/access anything within our
memory regions.

Fixes: 875b9fd97b34 ("Support individual region unmap in libvhost-user")
Cc: qemu-stable@nongnu.org
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Coiby Xu <coiby.xu@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 subprojects/libvhost-user/libvhost-user.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index bf09693255..787f4d2d4f 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -816,6 +816,7 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
             shadow_regions[j].gpa = dev->regions[i].gpa;
             shadow_regions[j].size = dev->regions[i].size;
             shadow_regions[j].qva = dev->regions[i].qva;
+            shadow_regions[j].mmap_addr = dev->regions[i].mmap_addr;
             shadow_regions[j].mmap_offset = dev->regions[i].mmap_offset;
             j++;
         } else {
-- 
2.31.1

Re: [PATCH v1] libvhost-user: fix VHOST_USER_REM_MEM_REG skipping mmap_addr

[Raphael Norwitz]

On Mon, Oct 11, 2021 at 10:10:47PM +0200, David Hildenbrand wrote:
> We end up not copying the mmap_addr of all existing regions, resulting
> in a SEGFAULT once we actually try to map/access anything within our
> memory regions.
> 
> Fixes: 875b9fd97b34 ("Support individual region unmap in libvhost-user")
> Cc: qemu-stable@nongnu.org
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
> Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Coiby Xu <coiby.xu@gmail.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>

> ---
>  subprojects/libvhost-user/libvhost-user.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> index bf09693255..787f4d2d4f 100644
> --- a/subprojects/libvhost-user/libvhost-user.c
> +++ b/subprojects/libvhost-user/libvhost-user.c
> @@ -816,6 +816,7 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
>              shadow_regions[j].gpa = dev->regions[i].gpa;
>              shadow_regions[j].size = dev->regions[i].size;
>              shadow_regions[j].qva = dev->regions[i].qva;
> +            shadow_regions[j].mmap_addr = dev->regions[i].mmap_addr;
>              shadow_regions[j].mmap_offset = dev->regions[i].mmap_offset;
>              j++;
>          } else {
> -- 
> 2.31.1
> 

Re: [PATCH v1] libvhost-user: fix VHOST_USER_REM_MEM_REG skipping mmap_addr

[Stefan Hajnoczi]

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On Mon, Oct 11, 2021 at 10:10:47PM +0200, David Hildenbrand wrote:
> We end up not copying the mmap_addr of all existing regions, resulting
> in a SEGFAULT once we actually try to map/access anything within our
> memory regions.
> 
> Fixes: 875b9fd97b34 ("Support individual region unmap in libvhost-user")
> Cc: qemu-stable@nongnu.org
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
> Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Coiby Xu <coiby.xu@gmail.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  subprojects/libvhost-user/libvhost-user.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> index bf09693255..787f4d2d4f 100644
> --- a/subprojects/libvhost-user/libvhost-user.c
> +++ b/subprojects/libvhost-user/libvhost-user.c
> @@ -816,6 +816,7 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
>              shadow_regions[j].gpa = dev->regions[i].gpa;
>              shadow_regions[j].size = dev->regions[i].size;
>              shadow_regions[j].qva = dev->regions[i].qva;
> +            shadow_regions[j].mmap_addr = dev->regions[i].mmap_addr;
>              shadow_regions[j].mmap_offset = dev->regions[i].mmap_offset;
>              j++;
>          } else {

Raphael: Some questions about vu_rem_mem_reg():

- What ensures that shadow_regions[VHOST_USER_MAX_RAM_SLOTS] is large
  enough? The add_mem_reg/set_mem_table code doesn't seem to check
  whether there is enough space in dev->regions[] before adding regions.

- What happens when the master populated dev->regions[] with multiple
  copies of the same region? dev->nregions is only decremented once and
  no longer accurately reflects the number of elements in
  dev->regions[].

libvhost-user must not trust the vhost-user master since vhost-user
needs to provide process isolation. Please add input validation.

Stefan

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Re: [PATCH v1] libvhost-user: fix VHOST_USER_REM_MEM_REG skipping mmap_addr

[Stefan Hajnoczi]

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On Mon, Oct 11, 2021 at 10:10:47PM +0200, David Hildenbrand wrote:
> We end up not copying the mmap_addr of all existing regions, resulting
> in a SEGFAULT once we actually try to map/access anything within our
> memory regions.
> 
> Fixes: 875b9fd97b34 ("Support individual region unmap in libvhost-user")
> Cc: qemu-stable@nongnu.org
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
> Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Coiby Xu <coiby.xu@gmail.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  subprojects/libvhost-user/libvhost-user.c | 1 +
>  1 file changed, 1 insertion(+)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [PATCH v1] libvhost-user: fix VHOST_USER_REM_MEM_REG skipping mmap_addr

[Raphael Norwitz]

On Wed, Oct 13, 2021 at 10:40:46AM +0100, Stefan Hajnoczi wrote:
> On Mon, Oct 11, 2021 at 10:10:47PM +0200, David Hildenbrand wrote:
> > We end up not copying the mmap_addr of all existing regions, resulting
> > in a SEGFAULT once we actually try to map/access anything within our
> > memory regions.
> > 
> > Fixes: 875b9fd97b34 ("Support individual region unmap in libvhost-user")
> > Cc: qemu-stable@nongnu.org
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
> > Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
> > Cc: Stefan Hajnoczi <stefanha@redhat.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Coiby Xu <coiby.xu@gmail.com>
> > Signed-off-by: David Hildenbrand <david@redhat.com>
> > ---
> >  subprojects/libvhost-user/libvhost-user.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> > index bf09693255..787f4d2d4f 100644
> > --- a/subprojects/libvhost-user/libvhost-user.c
> > +++ b/subprojects/libvhost-user/libvhost-user.c
> > @@ -816,6 +816,7 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> >              shadow_regions[j].gpa = dev->regions[i].gpa;
> >              shadow_regions[j].size = dev->regions[i].size;
> >              shadow_regions[j].qva = dev->regions[i].qva;
> > +            shadow_regions[j].mmap_addr = dev->regions[i].mmap_addr;
> >              shadow_regions[j].mmap_offset = dev->regions[i].mmap_offset;
> >              j++;
> >          } else {
> 
> Raphael: Some questions about vu_rem_mem_reg():
> 
> - What ensures that shadow_regions[VHOST_USER_MAX_RAM_SLOTS] is large
>   enough? The add_mem_reg/set_mem_table code doesn't seem to check
>   whether there is enough space in dev->regions[] before adding regions.
>

Correct - it does not check if there is enough space as is. I can add that.

> - What happens when the master populated dev->regions[] with multiple
>   copies of the same region? dev->nregions is only decremented once and
>   no longer accurately reflects the number of elements in
>   dev->regions[].

That case is also not accounted for. I will add it.

> 
> libvhost-user must not trust the vhost-user master since vhost-user
> needs to provide process isolation. Please add input validation.
> 

Got it - let me start working on a series.

> Stefan

Re: [PATCH v1] libvhost-user: fix VHOST_USER_REM_MEM_REG skipping mmap_addr

[Stefan Hajnoczi]

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On Thu, Oct 14, 2021 at 04:52:48AM +0000, Raphael Norwitz wrote:
> On Wed, Oct 13, 2021 at 10:40:46AM +0100, Stefan Hajnoczi wrote:
> > On Mon, Oct 11, 2021 at 10:10:47PM +0200, David Hildenbrand wrote:
> > > We end up not copying the mmap_addr of all existing regions, resulting
> > > in a SEGFAULT once we actually try to map/access anything within our
> > > memory regions.
> > > 
> > > Fixes: 875b9fd97b34 ("Support individual region unmap in libvhost-user")
> > > Cc: qemu-stable@nongnu.org
> > > Cc: Michael S. Tsirkin <mst@redhat.com>
> > > Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
> > > Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
> > > Cc: Stefan Hajnoczi <stefanha@redhat.com>
> > > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > > Cc: Coiby Xu <coiby.xu@gmail.com>
> > > Signed-off-by: David Hildenbrand <david@redhat.com>
> > > ---
> > >  subprojects/libvhost-user/libvhost-user.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> > > index bf09693255..787f4d2d4f 100644
> > > --- a/subprojects/libvhost-user/libvhost-user.c
> > > +++ b/subprojects/libvhost-user/libvhost-user.c
> > > @@ -816,6 +816,7 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> > >              shadow_regions[j].gpa = dev->regions[i].gpa;
> > >              shadow_regions[j].size = dev->regions[i].size;
> > >              shadow_regions[j].qva = dev->regions[i].qva;
> > > +            shadow_regions[j].mmap_addr = dev->regions[i].mmap_addr;
> > >              shadow_regions[j].mmap_offset = dev->regions[i].mmap_offset;
> > >              j++;
> > >          } else {
> > 
> > Raphael: Some questions about vu_rem_mem_reg():
> > 
> > - What ensures that shadow_regions[VHOST_USER_MAX_RAM_SLOTS] is large
> >   enough? The add_mem_reg/set_mem_table code doesn't seem to check
> >   whether there is enough space in dev->regions[] before adding regions.
> >
> 
> Correct - it does not check if there is enough space as is. I can add that.
> 
> > - What happens when the master populated dev->regions[] with multiple
> >   copies of the same region? dev->nregions is only decremented once and
> >   no longer accurately reflects the number of elements in
> >   dev->regions[].
> 
> That case is also not accounted for. I will add it.
> 
> > 
> > libvhost-user must not trust the vhost-user master since vhost-user
> > needs to provide process isolation. Please add input validation.
> > 
> 
> Got it - let me start working on a series.

Great, thank you!

Stefan

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Re: [PATCH v1] libvhost-user: fix VHOST_USER_REM_MEM_REG skipping mmap_addr

[Michael S. Tsirkin]

On Thu, Oct 14, 2021 at 04:52:48AM +0000, Raphael Norwitz wrote:
> On Wed, Oct 13, 2021 at 10:40:46AM +0100, Stefan Hajnoczi wrote:
> > On Mon, Oct 11, 2021 at 10:10:47PM +0200, David Hildenbrand wrote:
> > > We end up not copying the mmap_addr of all existing regions, resulting
> > > in a SEGFAULT once we actually try to map/access anything within our
> > > memory regions.
> > > 
> > > Fixes: 875b9fd97b34 ("Support individual region unmap in libvhost-user")
> > > Cc: qemu-stable@nongnu.org
> > > Cc: Michael S. Tsirkin <mst@redhat.com>
> > > Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
> > > Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
> > > Cc: Stefan Hajnoczi <stefanha@redhat.com>
> > > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > > Cc: Coiby Xu <coiby.xu@gmail.com>
> > > Signed-off-by: David Hildenbrand <david@redhat.com>
> > > ---
> > >  subprojects/libvhost-user/libvhost-user.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> > > index bf09693255..787f4d2d4f 100644
> > > --- a/subprojects/libvhost-user/libvhost-user.c
> > > +++ b/subprojects/libvhost-user/libvhost-user.c
> > > @@ -816,6 +816,7 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> > >              shadow_regions[j].gpa = dev->regions[i].gpa;
> > >              shadow_regions[j].size = dev->regions[i].size;
> > >              shadow_regions[j].qva = dev->regions[i].qva;
> > > +            shadow_regions[j].mmap_addr = dev->regions[i].mmap_addr;
> > >              shadow_regions[j].mmap_offset = dev->regions[i].mmap_offset;
> > >              j++;
> > >          } else {
> > 
> > Raphael: Some questions about vu_rem_mem_reg():
> > 
> > - What ensures that shadow_regions[VHOST_USER_MAX_RAM_SLOTS] is large
> >   enough? The add_mem_reg/set_mem_table code doesn't seem to check
> >   whether there is enough space in dev->regions[] before adding regions.
> >
> 
> Correct - it does not check if there is enough space as is. I can add that.


Just making sure - you are now working on series supreceding this patch?
Is that right?

> > - What happens when the master populated dev->regions[] with multiple
> >   copies of the same region? dev->nregions is only decremented once and
> >   no longer accurately reflects the number of elements in
> >   dev->regions[].
> 
> That case is also not accounted for. I will add it.
> 
> > 
> > libvhost-user must not trust the vhost-user master since vhost-user
> > needs to provide process isolation. Please add input validation.
> > 
> 
> Got it - let me start working on a series.
> 
> > Stefan

Re: [PATCH v1] libvhost-user: fix VHOST_USER_REM_MEM_REG skipping mmap_addr

[Raphael Norwitz]

On Mon, Oct 18, 2021 at 09:49:53AM -0400, Michael S. Tsirkin wrote:
> On Thu, Oct 14, 2021 at 04:52:48AM +0000, Raphael Norwitz wrote:
> > On Wed, Oct 13, 2021 at 10:40:46AM +0100, Stefan Hajnoczi wrote:
> > > On Mon, Oct 11, 2021 at 10:10:47PM +0200, David Hildenbrand wrote:
> > > > We end up not copying the mmap_addr of all existing regions, resulting
> > > > in a SEGFAULT once we actually try to map/access anything within our
> > > > memory regions.
> > > > 
> > > > Fixes: 875b9fd97b34 ("Support individual region unmap in libvhost-user")
> > > > Cc: qemu-stable@nongnu.org
> > > > Cc: Michael S. Tsirkin <mst@redhat.com>
> > > > Cc: Raphael Norwitz <raphael.norwitz@nutanix.com>
> > > > Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
> > > > Cc: Stefan Hajnoczi <stefanha@redhat.com>
> > > > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > > > Cc: Coiby Xu <coiby.xu@gmail.com>
> > > > Signed-off-by: David Hildenbrand <david@redhat.com>
> > > > ---
> > > >  subprojects/libvhost-user/libvhost-user.c | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > > 
> > > > diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> > > > index bf09693255..787f4d2d4f 100644
> > > > --- a/subprojects/libvhost-user/libvhost-user.c
> > > > +++ b/subprojects/libvhost-user/libvhost-user.c
> > > > @@ -816,6 +816,7 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> > > >              shadow_regions[j].gpa = dev->regions[i].gpa;
> > > >              shadow_regions[j].size = dev->regions[i].size;
> > > >              shadow_regions[j].qva = dev->regions[i].qva;
> > > > +            shadow_regions[j].mmap_addr = dev->regions[i].mmap_addr;
> > > >              shadow_regions[j].mmap_offset = dev->regions[i].mmap_offset;
> > > >              j++;
> > > >          } else {
> > > 
> > > Raphael: Some questions about vu_rem_mem_reg():
> > > 
> > > - What ensures that shadow_regions[VHOST_USER_MAX_RAM_SLOTS] is large
> > >   enough? The add_mem_reg/set_mem_table code doesn't seem to check
> > >   whether there is enough space in dev->regions[] before adding regions.
> > >
> > 
> > Correct - it does not check if there is enough space as is. I can add that.
> 
> 
> Just making sure - you are now working on series supreceding this patch?
> Is that right?

I was just going to fix the missing input validation. This looks like a
standalone issue and in my opinon the fix should go in as is. I will
base my changes on top of it. 

> 
> > > - What happens when the master populated dev->regions[] with multiple
> > >   copies of the same region? dev->nregions is only decremented once and
> > >   no longer accurately reflects the number of elements in
> > >   dev->regions[].
> > 
> > That case is also not accounted for. I will add it.
> > 
> > > 
> > > libvhost-user must not trust the vhost-user master since vhost-user
> > > needs to provide process isolation. Please add input validation.
> > > 
> > 
> > Got it - let me start working on a series.
> > 
> > > Stefan
>