The sg list/indirect descriptor table may be contigious
in GPA but not in HVA address space. But libvhost-user
wasn't aware of that. This would cause out-of-bounds
access. Even a malicious guest could use it to get
information from the vhost-user backend.
Introduce a plen parameter in vu_gpa_to_va() so we can
handle this case, returning the actual mapped length.
Signed-off-by: Yongji Xie <xieyon...@baidu.com>
---
contrib/libvhost-user/libvhost-user.c | 133 +++++++++++++++++++++++++++++----
contrib/libvhost-user/libvhost-user.h | 3 +-
2 files changed, 122 insertions(+), 14 deletions(-)
diff --git a/contrib/libvhost-user/libvhost-user.c
b/contrib/libvhost-user/libvhost-user.c
index cadced7..6ec31c6 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -116,15 +116,22 @@ vu_panic(VuDev *dev, const char *msg, ...)
/* Translate guest physical address to our virtual address. */
void *
-vu_gpa_to_va(VuDev *dev, uint64_t guest_addr)
+vu_gpa_to_va(VuDev *dev, uint64_t *plen, uint64_t guest_addr)
{
int i;
+ if (*plen == 0) {
+ return NULL;
+ }
+
/* Find matching memory region. */
for (i = 0; i < dev->nregions; i++) {
VuDevRegion *r = &dev->regions[i];
if ((guest_addr >= r->gpa) && (guest_addr < (r->gpa + r->size))) {
+ if ((guest_addr + *plen) > (r->gpa + r->size)) {
+ *plen = r->gpa + r->size - guest_addr;
+ }
return (void *)(uintptr_t)
guest_addr - r->gpa + r->mmap_addr + r->mmap_offset;
}
@@ -1074,6 +1081,37 @@ virtqueue_get_head(VuDev *dev, VuVirtq *vq,
return true;
}
+static int
+virtqueue_read_indirect_desc(VuDev *dev, struct vring_desc *desc,
+ uint64_t addr, size_t len)
+{
+ struct vring_desc *ori_desc;
+ uint64_t read_len;
+
+ if (len > (VIRTQUEUE_MAX_SIZE * sizeof(struct vring_desc))) {
+ return -1;
+ }
+
+ if (len == 0) {
+ return -1;
+ }
+
+ while (len) {
+ read_len = len;
+ ori_desc = vu_gpa_to_va(dev, &read_len, addr);
+ if (!ori_desc) {
+ return -1;
+ }
+
+ memcpy(desc, ori_desc, read_len);
+ len -= read_len;
+ addr += read_len;
+ desc += read_len;
+ }
+
+ return 0;
+}
+
enum {
VIRTQUEUE_READ_DESC_ERROR = -1,
VIRTQUEUE_READ_DESC_DONE = 0, /* end of chain */
@@ -1120,8 +1158,10 @@ vu_queue_get_avail_bytes(VuDev *dev, VuVirtq *vq,
unsigned int *in_bytes,
}
while ((rc = virtqueue_num_heads(dev, vq, idx)) > 0) {
- unsigned int max, num_bufs, indirect = 0;
+ unsigned int max, desc_len, num_bufs, indirect = 0;
+ uint64_t desc_addr, read_len;
struct vring_desc *desc;
+ struct vring_desc desc_buf[VIRTQUEUE_MAX_SIZE];
unsigned int i;
max = vq->vring.num;
@@ -1145,8 +1185,24 @@ vu_queue_get_avail_bytes(VuDev *dev, VuVirtq *vq,
unsigned int *in_bytes,
/* loop over the indirect descriptor table */
indirect = 1;
- max = desc[i].len / sizeof(struct vring_desc);
- desc = vu_gpa_to_va(dev, desc[i].addr);
+ desc_addr = desc[i].addr;
+ desc_len = desc[i].len;
+ max = desc_len / sizeof(struct vring_desc);
+ read_len = desc_len;
+ desc = vu_gpa_to_va(dev, &read_len, desc_addr);
+ if (unlikely(desc && read_len != desc_len)) {
+ /* Failed to use zero copy */
+ desc = NULL;
+ if (!virtqueue_read_indirect_desc(dev, desc_buf,
+ desc_addr,
+ desc_len)) {
+ desc = desc_buf;
+ }
+ }
+ if (!desc) {
+ vu_panic(dev, "Invalid indirect buffer table");
+ goto err;
+ }
num_bufs = i = 0;
}
@@ -1344,9 +1400,24 @@ virtqueue_map_desc(VuDev *dev,
return;
}
- iov[num_sg].iov_base = vu_gpa_to_va(dev, pa);
- iov[num_sg].iov_len = sz;
- num_sg++;
+ while (sz) {
+ uint64_t len = sz;
+
+ if (num_sg == max_num_sg) {
+ vu_panic(dev, "virtio: too many descriptors in indirect table");
+ return;
+ }
+
+ iov[num_sg].iov_base = vu_gpa_to_va(dev, &len, pa);
+ if (iov[num_sg].iov_base == NULL) {
+ vu_panic(dev, "virtio: invalid address for buffers");
+ return;
+ }
+ iov[num_sg].iov_len = len;
+ num_sg++;
+ sz -= len;
+ pa += len;
+ }
*p_num_sg = num_sg;
}
@@ -1378,10 +1449,12 @@ virtqueue_alloc_element(size_t sz,
void *
vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz)
{
- unsigned int i, head, max;
+ unsigned int i, head, max, desc_len;
+ uint64_t desc_addr, read_len;
VuVirtqElement *elem;
unsigned out_num, in_num;
struct iovec iov[VIRTQUEUE_MAX_SIZE];
+ struct vring_desc desc_buf[VIRTQUEUE_MAX_SIZE];
struct vring_desc *desc;
int rc;
@@ -1422,8 +1495,24 @@ vu_queue_pop(VuDev *dev, VuVirtq *vq, size_t sz)
}
/* loop over the indirect descriptor table */
- max = desc[i].len / sizeof(struct vring_desc);
- desc = vu_gpa_to_va(dev, desc[i].addr);
+ desc_addr = desc[i].addr;
+ desc_len = desc[i].len;
+ max = desc_len / sizeof(struct vring_desc);
+ read_len = desc_len;
+ desc = vu_gpa_to_va(dev, &read_len, desc_addr);
+ if (unlikely(desc && read_len != desc_len)) {
+ /* Failed to use zero copy */
+ desc = NULL;
+ if (!virtqueue_read_indirect_desc(dev, desc_buf,
+ desc_addr,
+ desc_len)) {
+ desc = desc_buf;
+ }
+ }
+ if (!desc) {
+ vu_panic(dev, "Invalid indirect buffer table");
+ return NULL;
+ }
i = 0;
}
@@ -1499,7 +1588,9 @@ vu_log_queue_fill(VuDev *dev, VuVirtq *vq,
unsigned int len)
{
struct vring_desc *desc = vq->vring.desc;
- unsigned int i, max, min;
+ unsigned int i, max, min, desc_len;
+ uint64_t desc_addr, read_len;
+ struct vring_desc desc_buf[VIRTQUEUE_MAX_SIZE];
unsigned num_bufs = 0;
max = vq->vring.num;
@@ -1511,8 +1602,24 @@ vu_log_queue_fill(VuDev *dev, VuVirtq *vq,
}
/* loop over the indirect descriptor table */
- max = desc[i].len / sizeof(struct vring_desc);
- desc = vu_gpa_to_va(dev, desc[i].addr);
+ desc_addr = desc[i].addr;
+ desc_len = desc[i].len;
+ max = desc_len / sizeof(struct vring_desc);
+ read_len = desc_len;
+ desc = vu_gpa_to_va(dev, &read_len, desc_addr);
+ if (unlikely(desc && read_len != desc_len)) {
+ /* Failed to use zero copy */
+ desc = NULL;
+ if (!virtqueue_read_indirect_desc(dev, desc_buf,
+ desc_addr,
+ desc_len)) {
+ desc = desc_buf;
+ }
+ }
+ if (!desc) {
+ vu_panic(dev, "Invalid indirect buffer table");
+ return;
+ }
i = 0;
}
diff --git a/contrib/libvhost-user/libvhost-user.h
b/contrib/libvhost-user/libvhost-user.h
index 2f5864b..4e7ecd8 100644
--- a/contrib/libvhost-user/libvhost-user.h
+++ b/contrib/libvhost-user/libvhost-user.h
@@ -294,11 +294,12 @@ bool vu_dispatch(VuDev *dev);
/**
* vu_gpa_to_va:
* @dev: a VuDev context
+ * @plen: guest memory size
* @guest_addr: guest address
*
* Translate a guest address to a pointer. Returns NULL on failure.
*/
-void *vu_gpa_to_va(VuDev *dev, uint64_t guest_addr);
+void *vu_gpa_to_va(VuDev *dev, uint64_t *plen, uint64_t guest_addr);
/**
* vu_get_queue:
--
1.7.9.5
