On 2020/10/9 上午4:42, Stefano Garzarella wrote:
If riov and wiov are both defined and they point to different
objects, only riov is initialized. If the wiov is not initialized
by the caller, the function fails returning -EINVAL and printing
"Readable desc 0x... after writable" error message.
This issue happens when descriptors have both readable and writable
buffers (eg. virtio-blk devices has virtio_blk_outhdr in the readable
buffer and status as last byte of writable buffer) and we call
__vringh_iov() to get both type of buffers in two different iovecs.
Let's replace the 'else if' clause with 'if' to initialize both
riov and wiov if they are not NULL.
As checkpatch pointed out, we also avoid crashing the kernel
when riov and wiov are both NULL, replacing BUG() with WARN_ON()
and returning -EINVAL.
It looks like I met the exact similar issue when developing ctrl vq
support (which requires both READ and WRITE descriptor).
While I was trying to fix the issue I found the following comment:
* Note that you may need to clean up riov and wiov, even on error!
*/
int vringh_getdesc_iotlb(struct vringh *vrh,
I saw some driver call vringh_kiov_cleanup().
So I just follow to use that.
I'm not quite sure which one is better.
Thanks
Fixes: f87d0fbb5798 ("vringh: host-side implementation of virtio rings.")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
---
drivers/vhost/vringh.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index e059a9a47cdf..8bd8b403f087 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -284,13 +284,14 @@ __vringh_iov(struct vringh *vrh, u16 i,
desc_max = vrh->vring.num;
up_next = -1;
+ /* You must want something! */
+ if (WARN_ON(!riov && !wiov))
+ return -EINVAL;
+
if (riov)
riov->i = riov->used = 0;
- else if (wiov)
+ if (wiov)
wiov->i = wiov->used = 0;
- else
- /* You must want something! */
- BUG();
for (;;) {
void *addr;
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