On Sun, Apr 28, 2013 at 03:54:20PM +0800, Jason Wang wrote:
> On 04/28/2013 03:26 AM, Michael S. Tsirkin wrote:
> > On Fri, Apr 26, 2013 at 04:34:02PM +0800, Jason Wang wrote:
> >> There are several several issues in the current checking:
> >>
> >> - The check was based on the minus of unsigned values which can overflow
> >> - It was done after .{set|get}_config() which can lead crash when
> >> config_len is
> >> zero since vdev->config is NULL
> >>
> >> Fix this by:
> >>
> >> - Validate the address in virtio_pci_config_{read|write}() before
> >> .{set|get}_config
> >> - Use addition instead minus to do the validation
> >>
> >> Cc: Michael S. Tsirkin <m...@redhat.com>
> >> Cc: Petr Matousek <pmato...@redhat.com>
> >> Signed-off-by: Jason Wang <jasow...@redhat.com>
> > Why do this in virtio-pci and not in virtio.c?
> > If instead we correct the checks in virtio.c we
> > get less code, and all transports will benefit
> > automatically.
>
> I wish I could but looks like vitio_config_read{b|w|l} were only used by
> virtio-pci. Other transport such as ccw and s390-virtio-bus have their
> own implementation.
Okay but still, the bug is in checks in virtio.c, why not fix it there
instead of making it assume caller does the checks?
> >
> >> ---
> >> hw/virtio/virtio-pci.c | 9 +++++++++
> >> hw/virtio/virtio.c | 18 ------------------
> >> 2 files changed, 9 insertions(+), 18 deletions(-)
> >>
> >> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> >> index a1f15a8..7f6c7d1 100644
> >> --- a/hw/virtio/virtio-pci.c
> >> +++ b/hw/virtio/virtio-pci.c
> >> @@ -400,6 +400,10 @@ static uint64_t virtio_pci_config_read(void *opaque,
> >> hwaddr addr,
> >> }
> >> addr -= config;
> >>
> >> + if (addr + size > proxy->vdev->config_len) {
> >> + return (uint32_t)-1;
> >> + }
> >> +
> >> switch (size) {
> >> case 1:
> >> val = virtio_config_readb(proxy->vdev, addr);
> >> @@ -430,6 +434,11 @@ static void virtio_pci_config_write(void *opaque,
> >> hwaddr addr,
> >> return;
> >> }
> >> addr -= config;
> >> +
> >> + if (addr + size > proxy->vdev->config_len) {
> >> + return;
> >> + }
> >> +
> >> /*
> >> * Virtio-PCI is odd. Ioports are LE but config space is target native
> >> * endian.
> >> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >> index 1c2282c..3397b5e 100644
> >> --- a/hw/virtio/virtio.c
> >> +++ b/hw/virtio/virtio.c
> >> @@ -563,9 +563,6 @@ uint32_t virtio_config_readb(VirtIODevice *vdev,
> >> uint32_t addr)
> >>
> >> vdev->get_config(vdev, vdev->config);
> >>
> >> - if (addr > (vdev->config_len - sizeof(val)))
> >> - return (uint32_t)-1;
> >> -
> >> val = ldub_p(vdev->config + addr);
> >> return val;
> >> }
> >> @@ -576,9 +573,6 @@ uint32_t virtio_config_readw(VirtIODevice *vdev,
> >> uint32_t addr)
> >>
> >> vdev->get_config(vdev, vdev->config);
> >>
> >> - if (addr > (vdev->config_len - sizeof(val)))
> >> - return (uint32_t)-1;
> >> -
> >> val = lduw_p(vdev->config + addr);
> >> return val;
> >> }
> >> @@ -589,9 +583,6 @@ uint32_t virtio_config_readl(VirtIODevice *vdev,
> >> uint32_t addr)
> >>
> >> vdev->get_config(vdev, vdev->config);
> >>
> >> - if (addr > (vdev->config_len - sizeof(val)))
> >> - return (uint32_t)-1;
> >> -
> >> val = ldl_p(vdev->config + addr);
> >> return val;
> >> }
> >> @@ -600,9 +591,6 @@ void virtio_config_writeb(VirtIODevice *vdev, uint32_t
> >> addr, uint32_t data)
> >> {
> >> uint8_t val = data;
> >>
> >> - if (addr > (vdev->config_len - sizeof(val)))
> >> - return;
> >> -
> >> stb_p(vdev->config + addr, val);
> >>
> >> if (vdev->set_config)
> >> @@ -613,9 +601,6 @@ void virtio_config_writew(VirtIODevice *vdev, uint32_t
> >> addr, uint32_t data)
> >> {
> >> uint16_t val = data;
> >>
> >> - if (addr > (vdev->config_len - sizeof(val)))
> >> - return;
> >> -
> >> stw_p(vdev->config + addr, val);
> >>
> >> if (vdev->set_config)
> >> @@ -626,9 +611,6 @@ void virtio_config_writel(VirtIODevice *vdev, uint32_t
> >> addr, uint32_t data)
> >> {
> >> uint32_t val = data;
> >>
> >> - if (addr > (vdev->config_len - sizeof(val)))
> >> - return;
> >> -
> >> stl_p(vdev->config + addr, val);
> >>
> >> if (vdev->set_config)
> >> --
> >> 1.7.1
