Re: [Qemu-devel] [PATCH 2/2] pci-assign: Fix memory out of bound when MSI-X table not fit in a single page

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Apr 03, 2014 at 01:18:24PM +0800, arei.gonglei@huawei.com wrote:
> From: Gonglei <arei.gonglei@huawei.com>
> 
> QEMU only mmap MSIX_PAGE_SIZE memory for all pci devices in
> assigned_dev_register_msix_mmio(), meanwhile the set the one
> page memmory to zero, so the rest memory will be random value
> (maybe etnry.data is not 0). In the assigned_dev_update_msix_mmio()
> maybe occur the issue of entry_nr > 256, and the kmod reports
> the EINVAL error.
> 
> Signed-off-by: Gonglei <arei.gonglei@huawei.com>

Okay so this kind of works because guest does not try
to use so many vectors.

But I think it's better not to give guest more entries
than we can actually support.

How about tweaking MSIX capability exposed to guest to limit table size?

> ---
>  hw/i386/kvm/pci-assign.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/i386/kvm/pci-assign.c b/hw/i386/kvm/pci-assign.c
> index 570333f..d25a19e 100644
> --- a/hw/i386/kvm/pci-assign.c
> +++ b/hw/i386/kvm/pci-assign.c
> @@ -37,6 +37,7 @@
>  #include "hw/pci/pci.h"
>  #include "hw/pci/msi.h"
>  #include "kvm_i386.h"
> +#include "qemu/osdep.h"
>  
>  #define MSIX_PAGE_SIZE 0x1000
>  
> @@ -59,6 +60,9 @@
>  #define DEBUG(fmt, ...)
>  #endif
>  
> +/* the msix-table size readed from pci device config */
> +static int msix_table_size;
> +
>  typedef struct PCIRegion {
>      int type;           /* Memory or port I/O */
>      int valid;
> @@ -1604,7 +1608,12 @@ static void assigned_dev_msix_reset(AssignedDevice *dev)
>  
>  static int assigned_dev_register_msix_mmio(AssignedDevice *dev)
>  {
> -    dev->msix_table = mmap(NULL, MSIX_PAGE_SIZE, PROT_READ|PROT_WRITE,
> +    msix_table_size = ROUND_UP(dev->msix_max * sizeof(struct MSIXTableEntry),
> +                                MSIX_PAGE_SIZE);
> +
> +    DEBUG("msix_table_size: 0x%x\n", msix_table_size);
> +
> +    dev->msix_table = mmap(NULL, msix_table_size, PROT_READ|PROT_WRITE,
>                             MAP_ANONYMOUS|MAP_PRIVATE, 0, 0);
>      if (dev->msix_table == MAP_FAILED) {
>          error_report("fail allocate msix_table! %s", strerror(errno));
> @@ -1615,7 +1624,7 @@ static int assigned_dev_register_msix_mmio(AssignedDevice *dev)
>      assigned_dev_msix_reset(dev);
>  
>      memory_region_init_io(&dev->mmio, OBJECT(dev), &assigned_dev_msix_mmio_ops,
> -                          dev, "assigned-dev-msix", MSIX_PAGE_SIZE);
> +                          dev, "assigned-dev-msix", msix_table_size);
>      return 0;
>  }
>  
> @@ -1627,7 +1636,7 @@ static void assigned_dev_unregister_msix_mmio(AssignedDevice *dev)
>  
>      memory_region_destroy(&dev->mmio);
>  
> -    if (munmap(dev->msix_table, MSIX_PAGE_SIZE) == -1) {
> +    if (munmap(dev->msix_table, msix_table_size) == -1) {
>          error_report("error unmapping msix_table! %s", strerror(errno));
>      }
>      dev->msix_table = NULL;
> -- 
> 1.7.12.4
> 
>