[PATCH 4.19 274/287] vringh: Fix loop descriptors check in the indirect cases

[Greg Kroah-Hartman]

From: Xie Yongji <xieyongji@xxxxxxxxxxxxx>

[ 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@xxxxxxxxxxxxx>
Signed-off-by: Fam Zheng <fam.zheng@xxxxxxxxxxxxx>
Message-Id: <20220505100910.137-1-xieyongji@xxxxxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/vhost/vringh.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 97aa9b87e572..6b2efff1c297 100644
--- 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;
 		}
-- 
2.35.1