vringh: Fix loop descriptors check in the indirect cases

[ Upstream commit dbd29e0752286af74243cf891accf472b2f3edd8 ]

We should use size of descriptor chain to test loop condition
in the indirect case. And another statistical count is also introduced
for indirect descriptors to avoid conflict with the statistical count
of direct descriptors.

Fixes: f87d0fbb5798 ("vringh: host-side implementation of virtio rings.")
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Signed-off-by: Fam Zheng <fam.zheng@bytedance.com>
Message-Id: <20220505100910.137-1-xieyongji@bytedance.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index c23045aa9873c53e66a15e97991ca245259b0981..a764d36c4d387d18b46b4fa87af55a1d3786e22a 100644 (file)
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -263,7 +263,7 @@ __vringh_iov(struct vringh *vrh, u16 i,
             gfp_t gfp,
             int (*copy)(void *dst, const void *src, size_t len))
 {
-       int err, count = 0, up_next, desc_max;
+       int err, count = 0, indirect_count = 0, up_next, desc_max;
        struct vring_desc desc, *descs;
        struct vringh_range range = { -1ULL, 0 }, slowrange;
        bool slow = false;
@@ -320,7 +320,12 @@ __vringh_iov(struct vringh *vrh, u16 i,
                        continue;
                }
 
-               if (count++ == vrh->vring.num) {
+               if (up_next == -1)
+                       count++;
+               else
+                       indirect_count++;
+
+               if (count > vrh->vring.num || indirect_count > desc_max) {
                        vringh_bad("Descriptor loop in %p", descs);
                        err = -ELOOP;
                        goto fail;
@@ -382,6 +387,7 @@ __vringh_iov(struct vringh *vrh, u16 i,
                                i = return_from_indirect(vrh, &up_next,
                                                         &descs, &desc_max);
                                slow = false;
+                               indirect_count = 0;
                        } else
                                break;
                }