vhost: fix possible dead loop in relay helpers

Fix a possible dead loop which may happen, e.g. when
driver created a loop in the desc list.

Fixes: b13ad2decc83 ("vhost: provide helpers for virtio ring relay")

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/lib/librte_vhost/vdpa.c b/lib/librte_vhost/vdpa.c
index 407d1c3..02083bb 100644 (file)
--- a/lib/librte_vhost/vdpa.c
+++ b/lib/librte_vhost/vdpa.c
@@ -157,6 +157,7 @@ rte_vdpa_relay_vring_avail(int vid, uint16_t qid, void *vring_m)
        struct vring_desc *idesc = NULL;
        struct vring *s_vring;
        uint64_t dlen;
+       uint32_t nr_descs;
        int ret;
        uint8_t perm;
 
@@ -183,9 +184,14 @@ rte_vdpa_relay_vring_avail(int vid, uint16_t qid, void *vring_m)
 
                s_vring->avail->ring[idx_m & (vq->size - 1)] = desc_id;
                desc_ring = vq->desc;
+               nr_descs = vq->size;
 
                if (vq->desc[desc_id].flags & VRING_DESC_F_INDIRECT) {
                        dlen = vq->desc[desc_id].len;
+                       nr_descs = dlen / sizeof(struct vring_desc);
+                       if (unlikely(nr_descs > vq->size))
+                               return -1;
+
                        desc_ring = (struct vring_desc *)(uintptr_t)
                                vhost_iova_to_vva(dev, vq,
                                                vq->desc[desc_id].addr, &dlen,
@@ -210,6 +216,8 @@ rte_vdpa_relay_vring_avail(int vid, uint16_t qid, void *vring_m)
                do {
                        if (unlikely(desc_id >= vq->size))
                                goto fail;
+                       if (unlikely(nr_descs-- == 0))
+                               goto fail;
                        desc = desc_ring[desc_id];
                        perm = desc.flags & VRING_DESC_F_WRITE ?
                                VHOST_ACCESS_WO : VHOST_ACCESS_RO;
@@ -252,6 +260,7 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m)
        struct vring_desc *idesc = NULL;
        struct vring *s_vring;
        uint64_t dlen;
+       uint32_t nr_descs;
        int ret;
 
        if (!dev || !vring_m)
@@ -276,12 +285,17 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m)
 
                desc_id = vq->used->ring[idx & (vq->size - 1)].id;
                desc_ring = vq->desc;
+               nr_descs = vq->size;
 
                if (unlikely(desc_id >= vq->size))
                        return -1;
 
                if (vq->desc[desc_id].flags & VRING_DESC_F_INDIRECT) {
                        dlen = vq->desc[desc_id].len;
+                       nr_descs = dlen / sizeof(struct vring_desc);
+                       if (unlikely(nr_descs > vq->size))
+                               return -1;
+
                        desc_ring = (struct vring_desc *)(uintptr_t)
                                vhost_iova_to_vva(dev, vq,
                                                vq->desc[desc_id].addr, &dlen,
@@ -306,6 +320,8 @@ rte_vdpa_relay_vring_used(int vid, uint16_t qid, void *vring_m)
                do {
                        if (unlikely(desc_id >= vq->size))
                                goto fail;
+                       if (unlikely(nr_descs-- == 0))
+                               goto fail;
                        desc = desc_ring[desc_id];
                        if (desc.flags & VRING_DESC_F_WRITE)
                                vhost_log_write(dev, desc.addr, desc.len);