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[PATCH] pci: assert configuration access is within bounds

P J P posted 1 patch 3 years, 11 months ago
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git fetch https://github.com/patchew-project/qemu tags/patchew/20200604113525.58898-1-ppandit@redhat.com
hw/pci/pci.c | 4 ++++
1 file changed, 4 insertions(+)
[PATCH] pci: assert configuration access is within bounds
Posted by P J P 3 years, 11 months ago 
From: Prasad J Pandit <pjp@fedoraproject.org>

While accessing PCI configuration bytes, assert that
'address + len' is within PCI configuration space.

Generally it is within bounds. This is more of a defensive
assert, in case a buggy device was to send 'address' which
may go out of bounds.

Suggested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/pci/pci.c | 4 ++++
 1 file changed, 4 insertions(+)

Update v1: defensive assert as separate patch
  -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00957.html
  -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00960.html

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 70c66965f5..7bf2ae6d92 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1381,6 +1381,8 @@ uint32_t pci_default_read_config(PCIDevice *d,
 {
     uint32_t val = 0;
 
+    assert(address + len <= pci_config_size(d));
+
     if (pci_is_express_downstream_port(d) &&
         ranges_overlap(address, len, d->exp.exp_cap + PCI_EXP_LNKSTA, 2)) {
         pcie_sync_bridge_lnk(d);
@@ -1394,6 +1396,8 @@ void pci_default_write_config(PCIDevice *d, uint32_t addr, uint32_t val_in, int
     int i, was_irq_disabled = pci_irq_disabled(d);
     uint32_t val = val_in;
 
+    assert(addr + l <= pci_config_size(d));
+
     for (i = 0; i < l; val >>= 8, ++i) {
         uint8_t wmask = d->wmask[addr + i];
         uint8_t w1cmask = d->w1cmask[addr + i];
-- 
2.26.2
Re: [PATCH] pci: assert configuration access is within bounds
Posted by Michael S. Tsirkin 3 years, 11 months ago 
On Thu, Jun 04, 2020 at 05:05:25PM +0530, P J P wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> While accessing PCI configuration bytes, assert that
> 'address + len' is within PCI configuration space.
> 
> Generally it is within bounds. This is more of a defensive
> assert, in case a buggy device was to send 'address' which
> may go out of bounds.
> 
> Suggested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  hw/pci/pci.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> Update v1: defensive assert as separate patch
>   -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00957.html
>   -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00960.html
> 
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index 70c66965f5..7bf2ae6d92 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -1381,6 +1381,8 @@ uint32_t pci_default_read_config(PCIDevice *d,
>  {
>      uint32_t val = 0;
>  
> +    assert(address + len <= pci_config_size(d));
> +
>      if (pci_is_express_downstream_port(d) &&
>          ranges_overlap(address, len, d->exp.exp_cap + PCI_EXP_LNKSTA, 2)) {
>          pcie_sync_bridge_lnk(d);
> @@ -1394,6 +1396,8 @@ void pci_default_write_config(PCIDevice *d, uint32_t addr, uint32_t val_in, int
>      int i, was_irq_disabled = pci_irq_disabled(d);
>      uint32_t val = val_in;
>  
> +    assert(addr + l <= pci_config_size(d));
> +
>      for (i = 0; i < l; val >>= 8, ++i) {
>          uint8_t wmask = d->wmask[addr + i];
>          uint8_t w1cmask = d->w1cmask[addr + i];
> -- 
> 2.26.2
Re: [PATCH] pci: assert configuration access is within bounds
Posted by Dr. David Alan Gilbert 3 years, 11 months ago 
* P J P (ppandit@redhat.com) wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> While accessing PCI configuration bytes, assert that
> 'address + len' is within PCI configuration space.
> 
> Generally it is within bounds. This is more of a defensive
> assert, in case a buggy device was to send 'address' which
> may go out of bounds.

Can a guest trigger this assert?

Dave

> Suggested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/pci/pci.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> Update v1: defensive assert as separate patch
>   -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00957.html
>   -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00960.html
> 
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index 70c66965f5..7bf2ae6d92 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -1381,6 +1381,8 @@ uint32_t pci_default_read_config(PCIDevice *d,
>  {
>      uint32_t val = 0;
>  
> +    assert(address + len <= pci_config_size(d));
> +
>      if (pci_is_express_downstream_port(d) &&
>          ranges_overlap(address, len, d->exp.exp_cap + PCI_EXP_LNKSTA, 2)) {
>          pcie_sync_bridge_lnk(d);
> @@ -1394,6 +1396,8 @@ void pci_default_write_config(PCIDevice *d, uint32_t addr, uint32_t val_in, int
>      int i, was_irq_disabled = pci_irq_disabled(d);
>      uint32_t val = val_in;
>  
> +    assert(addr + l <= pci_config_size(d));
> +
>      for (i = 0; i < l; val >>= 8, ++i) {
>          uint8_t wmask = d->wmask[addr + i];
>          uint8_t w1cmask = d->w1cmask[addr + i];
> -- 
> 2.26.2
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
Re: [PATCH] pci: assert configuration access is within bounds
Posted by Michael S. Tsirkin 3 years, 11 months ago 
On Thu, Jun 04, 2020 at 05:36:31PM +0100, Dr. David Alan Gilbert wrote:
> * P J P (ppandit@redhat.com) wrote:
> > From: Prasad J Pandit <pjp@fedoraproject.org>
> > 
> > While accessing PCI configuration bytes, assert that
> > 'address + len' is within PCI configuration space.
> > 
> > Generally it is within bounds. This is more of a defensive
> > assert, in case a buggy device was to send 'address' which
> > may go out of bounds.
> 
> Can a guest trigger this assert?
> 
> Dave

Shouldn't be able to, no.

> > Suggested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> > Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> > ---
> >  hw/pci/pci.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > Update v1: defensive assert as separate patch
> >   -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00957.html
> >   -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00960.html
> > 
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index 70c66965f5..7bf2ae6d92 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -1381,6 +1381,8 @@ uint32_t pci_default_read_config(PCIDevice *d,
> >  {
> >      uint32_t val = 0;
> >  
> > +    assert(address + len <= pci_config_size(d));
> > +
> >      if (pci_is_express_downstream_port(d) &&
> >          ranges_overlap(address, len, d->exp.exp_cap + PCI_EXP_LNKSTA, 2)) {
> >          pcie_sync_bridge_lnk(d);
> > @@ -1394,6 +1396,8 @@ void pci_default_write_config(PCIDevice *d, uint32_t addr, uint32_t val_in, int
> >      int i, was_irq_disabled = pci_irq_disabled(d);
> >      uint32_t val = val_in;
> >  
> > +    assert(addr + l <= pci_config_size(d));
> > +
> >      for (i = 0; i < l; val >>= 8, ++i) {
> >          uint8_t wmask = d->wmask[addr + i];
> >          uint8_t w1cmask = d->w1cmask[addr + i];
> > -- 
> > 2.26.2
> > 
> > 
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Patchew 2.1-devel-0870f84

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