* [dpdk-dev] [PATCH] vhost: fix double read of descriptor flags
[not found] <CGME20181205150935eucas1p11698df8ed58ff02a4326dd5780af4470@eucas1p1.samsung.com>
@ 2018-12-05 15:09 ` Ilya Maximets
2018-12-11 14:47 ` Maxime Coquelin
2018-12-11 18:33 ` Maxime Coquelin
0 siblings, 2 replies; 3+ messages in thread
From: Ilya Maximets @ 2018-12-05 15:09 UTC (permalink / raw)
To: dev, Maxime Coquelin
Cc: Tiwei Bie, Zhihong Wang, jfreimann, Ilya Maximets, stable
Flags could be updated in a separate process leading to the
inconsistent check.
Additionally, read marked as 'volatile' to highlight the shared
nature of the variable and avoid such issues in the future.
Fixes: d3211c98c456 ("vhost: add helpers for packed virtqueues")
Cc: stable@dpdk.org
Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
---
lib/librte_vhost/vhost.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 5218f1b12..84cbee2b6 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -393,8 +393,10 @@ vq_is_packed(struct virtio_net *dev)
static inline bool
desc_is_avail(struct vring_packed_desc *desc, bool wrap_counter)
{
- return wrap_counter == !!(desc->flags & VRING_DESC_F_AVAIL) &&
- wrap_counter != !!(desc->flags & VRING_DESC_F_USED);
+ uint16_t flags = *((volatile uint16_t *) &desc->flags);
+
+ return wrap_counter == !!(flags & VRING_DESC_F_AVAIL) &&
+ wrap_counter != !!(flags & VRING_DESC_F_USED);
}
#define VHOST_LOG_PAGE 4096
--
2.17.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [dpdk-dev] [PATCH] vhost: fix double read of descriptor flags
2018-12-05 15:09 ` [dpdk-dev] [PATCH] vhost: fix double read of descriptor flags Ilya Maximets
@ 2018-12-11 14:47 ` Maxime Coquelin
2018-12-11 18:33 ` Maxime Coquelin
1 sibling, 0 replies; 3+ messages in thread
From: Maxime Coquelin @ 2018-12-11 14:47 UTC (permalink / raw)
To: Ilya Maximets, dev; +Cc: Tiwei Bie, Zhihong Wang, jfreimann, stable
On 12/5/18 4:09 PM, Ilya Maximets wrote:
> Flags could be updated in a separate process leading to the
> inconsistent check.
>
> Additionally, read marked as 'volatile' to highlight the shared
> nature of the variable and avoid such issues in the future.
>
> Fixes: d3211c98c456 ("vhost: add helpers for packed virtqueues")
> Cc: stable@dpdk.org
>
> Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
> ---
> lib/librte_vhost/vhost.h | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 5218f1b12..84cbee2b6 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -393,8 +393,10 @@ vq_is_packed(struct virtio_net *dev)
> static inline bool
> desc_is_avail(struct vring_packed_desc *desc, bool wrap_counter)
> {
> - return wrap_counter == !!(desc->flags & VRING_DESC_F_AVAIL) &&
> - wrap_counter != !!(desc->flags & VRING_DESC_F_USED);
> + uint16_t flags = *((volatile uint16_t *) &desc->flags);
> +
> + return wrap_counter == !!(flags & VRING_DESC_F_AVAIL) &&
> + wrap_counter != !!(flags & VRING_DESC_F_USED);
> }
>
> #define VHOST_LOG_PAGE 4096
>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Thanks,
Maxime
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [dpdk-dev] [PATCH] vhost: fix double read of descriptor flags
2018-12-05 15:09 ` [dpdk-dev] [PATCH] vhost: fix double read of descriptor flags Ilya Maximets
2018-12-11 14:47 ` Maxime Coquelin
@ 2018-12-11 18:33 ` Maxime Coquelin
1 sibling, 0 replies; 3+ messages in thread
From: Maxime Coquelin @ 2018-12-11 18:33 UTC (permalink / raw)
To: Ilya Maximets, dev; +Cc: Tiwei Bie, Zhihong Wang, jfreimann, stable
On 12/5/18 4:09 PM, Ilya Maximets wrote:
> Flags could be updated in a separate process leading to the
> inconsistent check.
>
> Additionally, read marked as 'volatile' to highlight the shared
> nature of the variable and avoid such issues in the future.
>
> Fixes: d3211c98c456 ("vhost: add helpers for packed virtqueues")
> Cc: stable@dpdk.org
>
> Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
> ---
> lib/librte_vhost/vhost.h | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 5218f1b12..84cbee2b6 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -393,8 +393,10 @@ vq_is_packed(struct virtio_net *dev)
> static inline bool
> desc_is_avail(struct vring_packed_desc *desc, bool wrap_counter)
> {
> - return wrap_counter == !!(desc->flags & VRING_DESC_F_AVAIL) &&
> - wrap_counter != !!(desc->flags & VRING_DESC_F_USED);
> + uint16_t flags = *((volatile uint16_t *) &desc->flags);
> +
> + return wrap_counter == !!(flags & VRING_DESC_F_AVAIL) &&
> + wrap_counter != !!(flags & VRING_DESC_F_USED);
> }
>
> #define VHOST_LOG_PAGE 4096
>
Applied to dpdk-next-virtio.
Thanks,
Maxime
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-12-05 15:09 ` [dpdk-dev] [PATCH] vhost: fix double read of descriptor flags Ilya Maximets
2018-12-11 14:47 ` Maxime Coquelin
2018-12-11 18:33 ` Maxime Coquelin
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