Linux Virtualization - Feb 2019 - [PATCH net] vhost: correctly check the return value of translate_desc() in log_used()

When fail, translate_desc() returns negative value, otherwise the
number of iovs. So we should fail when the return value is negative
instead of a blindly check against zero.

Reported-by: Stephen Hemminger <stephen at networkplumber.org>
Fixes: cc5e71075947 ("vhost: log dirty page correctly")
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/vhost.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 24a129fcdd61..a2e5dc7716e2 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1788,7 +1788,7 @@ static int log_used(struct vhost_virtqueue *vq, u64
used_offset, u64 len)
 
 	ret = translate_desc(vq, (uintptr_t)vq->used + used_offset,
 			     len, iov, 64, VHOST_ACCESS_WO);
-	if (ret)
+	if (ret < 0)
 		return ret;
 
 	for (i = 0; i < ret; i++) {
-- 
2.17.1

On Fri, 15 Feb 2019 15:53:24 +0800
Jason Wang <jasowang at redhat.com> wrote:
> When fail, translate_desc() returns negative value, otherwise the
> number of iovs. So we should fail when the return value is negative
> instead of a blindly check against zero.
> 
> Reported-by: Stephen Hemminger <stephen at networkplumber.org>
> Fixes: cc5e71075947 ("vhost: log dirty page correctly")
> Signed-off-by: Jason Wang <jasowang at redhat.com>
Looks good. It is best to put the Addresses-Coverity-Id tag on these kind
of bug fixes so that the automated tools see it.

From: Jason Wang <jasowang at redhat.com>
Date: Fri, 15 Feb 2019 15:53:24 +0800
> When fail, translate_desc() returns negative value, otherwise the
> number of iovs. So we should fail when the return value is negative
> instead of a blindly check against zero.
> 
> Reported-by: Stephen Hemminger <stephen at networkplumber.org>
> Fixes: cc5e71075947 ("vhost: log dirty page correctly")
> Signed-off-by: Jason Wang <jasowang at redhat.com>
Jason, please put the Fixes tag first.

Thank you.

On Fri, Feb 15, 2019 at 03:53:24PM +0800, Jason Wang
wrote:
> When fail, translate_desc() returns negative value, otherwise the
> number of iovs. So we should fail when the return value is negative
> instead of a blindly check against zero.
> 
> Reported-by: Stephen Hemminger <stephen at networkplumber.org>
> Fixes: cc5e71075947 ("vhost: log dirty page correctly")
> Signed-off-by: Jason Wang <jasowang at redhat.com>
Acked-by: Michael S. Tsirkin <mst at redhat.com>

and I guess the log was backported to stable so we want
this backported too.
> ---
>  drivers/vhost/vhost.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 24a129fcdd61..a2e5dc7716e2 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -1788,7 +1788,7 @@ static int log_used(struct vhost_virtqueue *vq, u64
used_offset, u64 len)
>  
>  	ret = translate_desc(vq, (uintptr_t)vq->used + used_offset,
>  			     len, iov, 64, VHOST_ACCESS_WO);
> -	if (ret)
> +	if (ret < 0)
>  		return ret;
>  
>  	for (i = 0; i < ret; i++) {
> -- 
> 2.17.1

On 2019/2/16 ??2:03, David Miller wrote:
> From: Jason Wang<jasowang at redhat.com>
> Date: Fri, 15 Feb 2019 15:53:24 +0800
>
>> When fail, translate_desc() returns negative value, otherwise the
>> number of iovs. So we should fail when the return value is negative
>> instead of a blindly check against zero.
>>
>> Reported-by: Stephen Hemminger<stephen at networkplumber.org>
>> Fixes: cc5e71075947 ("vhost: log dirty page correctly")
>> Signed-off-by: Jason Wang<jasowang at redhat.com>
> Jason, please put the Fixes tag first.
>
> Thank you.

Ok. Will post V2.

Thanks

On 2019/2/16 ??12:45, Stephen Hemminger wrote:
> On Fri, 15 Feb 2019 15:53:24 +0800
> Jason Wang <jasowang at redhat.com> wrote:
>
>> When fail, translate_desc() returns negative value, otherwise the
>> number of iovs. So we should fail when the return value is negative
>> instead of a blindly check against zero.
>>
>> Reported-by: Stephen Hemminger <stephen at networkplumber.org>
>> Fixes: cc5e71075947 ("vhost: log dirty page correctly")
>> Signed-off-by: Jason Wang <jasowang at redhat.com>
> Looks good. It is best to put the Addresses-Coverity-Id tag on these kind
> of bug fixes so that the automated tools see it.

Ok. Will do this in V2.

Thanks