virtio: Sanitize config accesses
The handling of VIRTIO_PCI_O_CONFIG is prone to buffer access overflows.
This patch sanitizes this operation by using the newly added virtio op
get_config_size. Any access which goes beyond the config structure's
size is prevented and a failure is returned.
Additionally, PCI accesses which span more than a single byte are prevented
and a warning is printed because the implementation does not currently
support the behavior correctly.
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Martin Radev <martin.b.radev@gmail.com>
Link: https://lore.kernel.org/r/20220509203940.754644-5-martin.b.radev@gmail.com
Signed-off-by: Will Deacon <will@kernel.org>
diff --git a/include/kvm/virtio-9p.h b/include/kvm/virtio-9p.h
index 3ea7698..77c5062 100644
--- a/include/kvm/virtio-9p.h
+++ b/include/kvm/virtio-9p.h
@@ -44,6 +44,7 @@
struct virtio_device vdev;
struct rb_root fids;
+ size_t config_size;
struct virtio_9p_config *config;
u32 features;
diff --git a/include/kvm/virtio.h b/include/kvm/virtio.h
index 3a311f5..3880e74 100644
--- a/include/kvm/virtio.h
+++ b/include/kvm/virtio.h
@@ -184,6 +184,7 @@
struct virtio_ops {
u8 *(*get_config)(struct kvm *kvm, void *dev);
+ size_t (*get_config_size)(struct kvm *kvm, void *dev);
u32 (*get_host_features)(struct kvm *kvm, void *dev);
void (*set_guest_features)(struct kvm *kvm, void *dev, u32 features);
int (*get_vq_count)(struct kvm *kvm, void *dev);
diff --git a/virtio/9p.c b/virtio/9p.c
index ca83436..57cd6d0 100644
--- a/virtio/9p.c
+++ b/virtio/9p.c
@@ -1375,6 +1375,13 @@
return ((u8 *)(p9dev->config));
}
+static size_t get_config_size(struct kvm *kvm, void *dev)
+{
+ struct p9_dev *p9dev = dev;
+
+ return p9dev->config_size;
+}
+
static u32 get_host_features(struct kvm *kvm, void *dev)
{
return 1 << VIRTIO_9P_MOUNT_TAG;
@@ -1469,6 +1476,7 @@
struct virtio_ops p9_dev_virtio_ops = {
.get_config = get_config,
+ .get_config_size = get_config_size,
.get_host_features = get_host_features,
.set_guest_features = set_guest_features,
.init_vq = init_vq,
@@ -1568,7 +1576,9 @@
int virtio_9p__register(struct kvm *kvm, const char *root, const char *tag_name)
{
struct p9_dev *p9dev;
- int err = 0;
+ size_t tag_length;
+ size_t config_size;
+ int err;
p9dev = calloc(1, sizeof(*p9dev));
if (!p9dev)
@@ -1577,29 +1587,34 @@
if (!tag_name)
tag_name = VIRTIO_9P_DEFAULT_TAG;
- p9dev->config = calloc(1, sizeof(*p9dev->config) + strlen(tag_name));
+ tag_length = strlen(tag_name);
+ /* The tag_name zero byte is intentionally excluded */
+ config_size = sizeof(*p9dev->config) + tag_length;
+
+ p9dev->config = calloc(1, config_size);
if (p9dev->config == NULL) {
err = -ENOMEM;
goto free_p9dev;
}
+ p9dev->config_size = config_size;
strncpy(p9dev->root_dir, root, sizeof(p9dev->root_dir));
p9dev->root_dir[sizeof(p9dev->root_dir)-1] = '\x00';
- p9dev->config->tag_len = strlen(tag_name);
+ p9dev->config->tag_len = tag_length;
if (p9dev->config->tag_len > MAX_TAG_LEN) {
err = -EINVAL;
goto free_p9dev_config;
}
- memcpy(&p9dev->config->tag, tag_name, strlen(tag_name));
+ memcpy(&p9dev->config->tag, tag_name, tag_length);
list_add(&p9dev->list, &devs);
if (compat_id == -1)
compat_id = virtio_compat_add_message("virtio-9p", "CONFIG_NET_9P_VIRTIO");
- return err;
+ return 0;
free_p9dev_config:
free(p9dev->config);
diff --git a/virtio/balloon.c b/virtio/balloon.c
index 7c7b115..655a661 100644
--- a/virtio/balloon.c
+++ b/virtio/balloon.c
@@ -186,6 +186,13 @@
return ((u8 *)(&bdev->config));
}
+static size_t get_config_size(struct kvm *kvm, void *dev)
+{
+ struct bln_dev *bdev = dev;
+
+ return sizeof(bdev->config);
+}
+
static u32 get_host_features(struct kvm *kvm, void *dev)
{
return 1 << VIRTIO_BALLOON_F_STATS_VQ;
@@ -256,6 +263,7 @@
struct virtio_ops bln_dev_virtio_ops = {
.get_config = get_config,
+ .get_config_size = get_config_size,
.get_host_features = get_host_features,
.set_guest_features = set_guest_features,
.init_vq = init_vq,
diff --git a/virtio/blk.c b/virtio/blk.c
index 4d02d10..af71c0c 100644
--- a/virtio/blk.c
+++ b/virtio/blk.c
@@ -146,6 +146,13 @@
return ((u8 *)(&bdev->blk_config));
}
+static size_t get_config_size(struct kvm *kvm, void *dev)
+{
+ struct blk_dev *bdev = dev;
+
+ return sizeof(bdev->blk_config);
+}
+
static u32 get_host_features(struct kvm *kvm, void *dev)
{
struct blk_dev *bdev = dev;
@@ -291,6 +298,7 @@
static struct virtio_ops blk_dev_virtio_ops = {
.get_config = get_config,
+ .get_config_size = get_config_size,
.get_host_features = get_host_features,
.set_guest_features = set_guest_features,
.get_vq_count = get_vq_count,
diff --git a/virtio/console.c b/virtio/console.c
index e0b98df..dae6034 100644
--- a/virtio/console.c
+++ b/virtio/console.c
@@ -121,6 +121,13 @@
return ((u8 *)(&cdev->config));
}
+static size_t get_config_size(struct kvm *kvm, void *dev)
+{
+ struct con_dev *cdev = dev;
+
+ return sizeof(cdev->config);
+}
+
static u32 get_host_features(struct kvm *kvm, void *dev)
{
return 0;
@@ -216,6 +223,7 @@
static struct virtio_ops con_dev_virtio_ops = {
.get_config = get_config,
+ .get_config_size = get_config_size,
.get_host_features = get_host_features,
.set_guest_features = set_guest_features,
.get_vq_count = get_vq_count,
diff --git a/virtio/mmio.c b/virtio/mmio.c
index 875a288..53519c1 100644
--- a/virtio/mmio.c
+++ b/virtio/mmio.c
@@ -103,15 +103,25 @@
u8 is_write, struct virtio_device *vdev)
{
struct virtio_mmio *vmmio = vdev->virtio;
+ u8 *config;
+ size_t config_size;
u32 i;
+ config = vdev->ops->get_config(vmmio->kvm, vmmio->dev);
+ config_size = vdev->ops->get_config_size(vmmio->kvm, vmmio->dev);
+
+ /* Prevent invalid accesses which go beyond the config */
+ if (config_size < addr + len) {
+ WARN_ONCE(1, "Offset (%llu) Length (%u) goes beyond config size (%zu).\n",
+ addr, len, config_size);
+ return;
+ }
+
for (i = 0; i < len; i++) {
if (is_write)
- vdev->ops->get_config(vmmio->kvm, vmmio->dev)[addr + i] =
- *(u8 *)data + i;
+ config[addr + i] = *(u8 *)data + i;
else
- data[i] = vdev->ops->get_config(vmmio->kvm,
- vmmio->dev)[addr + i];
+ data[i] = config[addr + i];
}
}
diff --git a/virtio/net.c b/virtio/net.c
index 1ee3c19..ec5dc1f 100644
--- a/virtio/net.c
+++ b/virtio/net.c
@@ -480,6 +480,13 @@
return ((u8 *)(&ndev->config));
}
+static size_t get_config_size(struct kvm *kvm, void *dev)
+{
+ struct net_dev *ndev = dev;
+
+ return sizeof(ndev->config);
+}
+
static u32 get_host_features(struct kvm *kvm, void *dev)
{
u32 features;
@@ -757,6 +764,7 @@
static struct virtio_ops net_dev_virtio_ops = {
.get_config = get_config,
+ .get_config_size = get_config_size,
.get_host_features = get_host_features,
.set_guest_features = set_guest_features,
.get_vq_count = get_vq_count,
diff --git a/virtio/pci.c b/virtio/pci.c
index bcb205a..050cfea 100644
--- a/virtio/pci.c
+++ b/virtio/pci.c
@@ -136,7 +136,21 @@
return true;
} else if (type == VIRTIO_PCI_O_CONFIG) {
u8 cfg;
+ size_t config_size;
+ config_size = vdev->ops->get_config_size(kvm, vpci->dev);
+ if (config_offset + size > config_size) {
+ /* Access goes beyond the config size, so return failure. */
+ WARN_ONCE(1, "Config access offset (%u) is beyond config size (%zu)\n",
+ config_offset, config_size);
+ return false;
+ }
+
+ /* TODO: Handle access lengths beyond one byte */
+ if (size != 1) {
+ WARN_ONCE(1, "Size (%u) not supported\n", size);
+ return false;
+ }
cfg = vdev->ops->get_config(kvm, vpci->dev)[config_offset];
ioport__write8(data, cfg);
return true;
@@ -276,6 +290,21 @@
return true;
} else if (type == VIRTIO_PCI_O_CONFIG) {
+ size_t config_size;
+
+ config_size = vdev->ops->get_config_size(kvm, vpci->dev);
+ if (config_offset + size > config_size) {
+ /* Access goes beyond the config size, so return failure. */
+ WARN_ONCE(1, "Config access offset (%u) is beyond config size (%zu)\n",
+ config_offset, config_size);
+ return false;
+ }
+
+ /* TODO: Handle access lengths beyond one byte */
+ if (size != 1) {
+ WARN_ONCE(1, "Size (%u) not supported\n", size);
+ return false;
+ }
vdev->ops->get_config(kvm, vpci->dev)[config_offset] = *(u8 *)data;
return true;
diff --git a/virtio/rng.c b/virtio/rng.c
index 78eaa64..c7835a0 100644
--- a/virtio/rng.c
+++ b/virtio/rng.c
@@ -47,6 +47,11 @@
return 0;
}
+static size_t get_config_size(struct kvm *kvm, void *dev)
+{
+ return 0;
+}
+
static u32 get_host_features(struct kvm *kvm, void *dev)
{
/* Unused */
@@ -149,6 +154,7 @@
static struct virtio_ops rng_dev_virtio_ops = {
.get_config = get_config,
+ .get_config_size = get_config_size,
.get_host_features = get_host_features,
.set_guest_features = set_guest_features,
.init_vq = init_vq,
diff --git a/virtio/scsi.c b/virtio/scsi.c
index 16a86cb..8f1c348 100644
--- a/virtio/scsi.c
+++ b/virtio/scsi.c
@@ -38,6 +38,13 @@
return ((u8 *)(&sdev->config));
}
+static size_t get_config_size(struct kvm *kvm, void *dev)
+{
+ struct scsi_dev *sdev = dev;
+
+ return sizeof(sdev->config);
+}
+
static u32 get_host_features(struct kvm *kvm, void *dev)
{
return 1UL << VIRTIO_RING_F_EVENT_IDX |
@@ -176,6 +183,7 @@
static struct virtio_ops scsi_dev_virtio_ops = {
.get_config = get_config,
+ .get_config_size = get_config_size,
.get_host_features = get_host_features,
.set_guest_features = set_guest_features,
.init_vq = init_vq,
diff --git a/virtio/vsock.c b/virtio/vsock.c
index 5b99838..34397b6 100644
--- a/virtio/vsock.c
+++ b/virtio/vsock.c
@@ -41,6 +41,13 @@
return ((u8 *)(&vdev->config));
}
+static size_t get_config_size(struct kvm *kvm, void *dev)
+{
+ struct vsock_dev *vdev = dev;
+
+ return sizeof(vdev->config);
+}
+
static u32 get_host_features(struct kvm *kvm, void *dev)
{
return 1UL << VIRTIO_RING_F_EVENT_IDX
@@ -204,6 +211,7 @@
static struct virtio_ops vsock_dev_virtio_ops = {
.get_config = get_config,
+ .get_config_size = get_config_size,
.get_host_features = get_host_features,
.set_guest_features = set_guest_features,
.init_vq = init_vq,
