Virtualization - Nov 2022 - [PATCH 2/2] vhost: fix range used in translate_desc()

While I was working on vringh to support VA in vringh_*_iotlb()
I saw that the range we use in iotlb_translate() when we call
vhost_iotlb_itree_first() was not correct IIUC.
So I looked at all the calls and found that in vhost.c as well.

I didn't observe a failure and I don't have a reproducer because
I noticed the problem by looking at the code.

Maybe we didn't have a problem, because a shorter range was being
returned anyway and the loop stopped taking into account the total
amount of bytes translated, but I think it's better to fix.

Thanks,
Stefano

Stefano Garzarella (2):
  vringh: fix range used in iotlb_translate()
  vhost: fix range used in translate_desc()

 drivers/vhost/vhost.c  | 4 ++--
 drivers/vhost/vringh.c | 5 ++---
 2 files changed, 4 insertions(+), 5 deletions(-)

-- 
2.38.1

vhost_iotlb_itree_first() requires `start` and `last` parameters
to search for a mapping that overlaps the range.

In iotlb_translate() we cyclically call vhost_iotlb_itree_first(),
incrementing `addr` by the amount already translated, so rightly
we move the `start` parameter passed to vhost_iotlb_itree_first(),
but we should hold the `last` parameter constant.

Let's fix it by saving the `last` parameter value before incrementing
`addr` in the loop.

Fixes: 9ad9c49cfe97 ("vringh: IOTLB support")
Signed-off-by: Stefano Garzarella <sgarzare at redhat.com>
---
 drivers/vhost/vringh.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 11f59dd06a74..828c29306565 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -1102,7 +1102,7 @@ static int iotlb_translate(const struct vringh *vrh,
 	struct vhost_iotlb_map *map;
 	struct vhost_iotlb *iotlb = vrh->iotlb;
 	int ret = 0;
-	u64 s = 0;
+	u64 s = 0, last = addr + len - 1;
 
 	spin_lock(vrh->iotlb_lock);
 
@@ -1114,8 +1114,7 @@ static int iotlb_translate(const struct vringh *vrh,
 			break;
 		}
 
-		map = vhost_iotlb_itree_first(iotlb, addr,
-					      addr + len - 1);
+		map = vhost_iotlb_itree_first(iotlb, addr, last);
 		if (!map || map->start > addr) {
 			ret = -EINVAL;
 			break;
-- 
2.38.1

vhost_iotlb_itree_first() requires `start` and `last` parameters
to search for a mapping that overlaps the range.

In translate_desc() we cyclically call vhost_iotlb_itree_first(),
incrementing `addr` by the amount already translated, so rightly
we move the `start` parameter passed to vhost_iotlb_itree_first(),
but we should hold the `last` parameter constant.

Let's fix it by saving the `last` parameter value before incrementing
`addr` in the loop.

Fixes: 0bbe30668d89 ("vhost: factor out IOTLB")
Signed-off-by: Stefano Garzarella <sgarzare at redhat.com>
---

I'm not sure about the fixes tag. On the one I used this patch should
apply cleanly, but looking at the latest stable (4.9), maybe we should
use

Fixes: a9709d6874d5 ("vhost: convert pre sorted vhost memory array to
interval tree")

Suggestions?
---
 drivers/vhost/vhost.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 40097826cff0..3c2359570df9 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2053,7 +2053,7 @@ static int translate_desc(struct vhost_virtqueue *vq, u64
addr, u32 len,
 	struct vhost_dev *dev = vq->dev;
 	struct vhost_iotlb *umem = dev->iotlb ? dev->iotlb : dev->umem;
 	struct iovec *_iov;
-	u64 s = 0;
+	u64 s = 0, last = addr + len - 1;
 	int ret = 0;
 
 	while ((u64)len > s) {
@@ -2063,7 +2063,7 @@ static int translate_desc(struct vhost_virtqueue *vq, u64
addr, u32 len,
 			break;
 		}
 
-		map = vhost_iotlb_itree_first(umem, addr, addr + len - 1);
+		map = vhost_iotlb_itree_first(umem, addr, last);
 		if (map == NULL || map->start > addr) {
 			if (umem != dev->iotlb) {
 				ret = -EFAULT;
-- 
2.38.1