thr3ads.net - Linux Virtualization - [PATCH net V2 3/4] Revert "net: vhost: lock the vqs one by one" [Dec 2018]

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Jason Wang

2018-Dec-12 10:08 UTC

[PATCH net V2 0/4] Fix various issue of vhost

Hi:

This series tries to fix various issues of vhost:

- Patch 1 adds a missing write barrier between used idx updating and
  logging.
- Patch 2-3 brings back the protection of device IOTLB through vq
  mutex, this fixes possible use after free in device IOTLB entries.
- Patch 4-7 fixes the diry page logging when device IOTLB is
  enabled. We should done through GPA instead of GIOVA, this was done
  through intorudce HVA->GPA reverse mapping and convert HVA to GPA
  during logging dirty pages.

Please consider them for -stable.

Thanks

Changes from V1:
- silent compiler warning for 32bit.
- use mutex_trylock() on slowpath instead of mutex_lock() even on fast
  path.

Jason Wang (4):
  vhost: make sure used idx is seen before log in vhost_add_used_n()
  vhost_net: switch to use mutex_trylock() in vhost_net_busy_poll()
  Revert "net: vhost: lock the vqs one by one"
  vhost: log dirty page correctly

 drivers/vhost/net.c   |  11 ++++-
 drivers/vhost/vhost.c | 102 ++++++++++++++++++++++++++++++++++--------
 drivers/vhost/vhost.h |   3 +-
 3 files changed, 95 insertions(+), 21 deletions(-)

-- 
2.17.1

Jason Wang

2018-Dec-12 10:08 UTC

head link

[PATCH net V2 1/4] vhost: make sure used idx is seen before log in vhost_add_used_n()

We miss a write barrier that guarantees used idx is updated and seen
before log. This will let userspace sync and copy used ring before
used idx is update. Fix this by adding a barrier before log_write().

Fixes: 8dd014adfea6f ("vhost-net: mergeable buffers support")
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/vhost.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 6b98d8e3a5bf..5915f240275a 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2220,6 +2220,8 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct
vring_used_elem *heads,
 		return -EFAULT;
 	}
 	if (unlikely(vq->log_used)) {
+		/* Make sure used idx is seen before log. */
+		smp_wmb();
 		/* Log used index update. */
 		log_write(vq->log_base,
 			  vq->log_addr + offsetof(struct vring_used, idx),
-- 
2.17.1

Jason Wang

2018-Dec-12 10:08 UTC

head link

[PATCH net V2 2/4] vhost_net: switch to use mutex_trylock() in vhost_net_busy_poll()

We used to hold the mutex of paired virtqueue in
vhost_net_busy_poll(). But this will results an inconsistent lock
order which may cause deadlock if we try to bring back the protection
of device IOTLB with vq mutex that requires to hold mutex of all
virtqueues at the same time.

Fix this simply by switching to use mutex_trylock(), when fail just
skip the busy polling. This can happen when device IOTLB is under
updating which should be rare.

Fixes: commit 78139c94dc8c ("net: vhost: lock the vqs one by one")
Cc: Tonghao Zhang <xiangxia.m.yue at gmail.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/net.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index ab11b2bee273..ad7a6f475a44 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -513,7 +513,13 @@ static void vhost_net_busy_poll(struct vhost_net *net,
 	struct socket *sock;
 	struct vhost_virtqueue *vq = poll_rx ? tvq : rvq;
 
-	mutex_lock_nested(&vq->mutex, poll_rx ? VHOST_NET_VQ_TX:
VHOST_NET_VQ_RX);
+	/* Try to hold the vq mutex of the paired virtqueue. We can't
+	 * use mutex_lock() here since we could not guarantee a
+	 * consistenet lock ordering.
+	 */
+	if (!mutex_trylock(&vq->mutex))
+		return;
+
 	vhost_disable_notify(&net->dev, vq);
 	sock = rvq->private_data;
 
-- 
2.17.1

Jason Wang

2018-Dec-12 10:08 UTC

head link

[PATCH net V2 3/4] Revert "net: vhost: lock the vqs one by one"

This reverts commit 78139c94dc8c96a478e67dab3bee84dc6eccb5fd. We don't
protect device IOTLB with vq mutex, which will lead e.g use after free
for device IOTLB entries. And since we've switched to use
mutex_trylock() in previous patch, it's safe to revert it without
having deadlock.

Fixes: commit 78139c94dc8c ("net: vhost: lock the vqs one by one")
Cc: Tonghao Zhang <xiangxia.m.yue at gmail.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/vhost.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 5915f240275a..55e5aa662ad5 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -295,11 +295,8 @@ static void vhost_vq_meta_reset(struct vhost_dev *d)
 {
 	int i;
 
-	for (i = 0; i < d->nvqs; ++i) {
-		mutex_lock(&d->vqs[i]->mutex);
+	for (i = 0; i < d->nvqs; ++i)
 		__vhost_vq_meta_reset(d->vqs[i]);
-		mutex_unlock(&d->vqs[i]->mutex);
-	}
 }
 
 static void vhost_vq_reset(struct vhost_dev *dev,
@@ -895,6 +892,20 @@ static inline void __user *__vhost_get_user(struct
vhost_virtqueue *vq,
 #define vhost_get_used(vq, x, ptr) \
 	vhost_get_user(vq, x, ptr, VHOST_ADDR_USED)
 
+static void vhost_dev_lock_vqs(struct vhost_dev *d)
+{
+	int i = 0;
+	for (i = 0; i < d->nvqs; ++i)
+		mutex_lock_nested(&d->vqs[i]->mutex, i);
+}
+
+static void vhost_dev_unlock_vqs(struct vhost_dev *d)
+{
+	int i = 0;
+	for (i = 0; i < d->nvqs; ++i)
+		mutex_unlock(&d->vqs[i]->mutex);
+}
+
 static int vhost_new_umem_range(struct vhost_umem *umem,
 				u64 start, u64 size, u64 end,
 				u64 userspace_addr, int perm)
@@ -976,6 +987,7 @@ static int vhost_process_iotlb_msg(struct vhost_dev *dev,
 	int ret = 0;
 
 	mutex_lock(&dev->mutex);
+	vhost_dev_lock_vqs(dev);
 	switch (msg->type) {
 	case VHOST_IOTLB_UPDATE:
 		if (!dev->iotlb) {
@@ -1009,6 +1021,7 @@ static int vhost_process_iotlb_msg(struct vhost_dev *dev,
 		break;
 	}
 
+	vhost_dev_unlock_vqs(dev);
 	mutex_unlock(&dev->mutex);
 
 	return ret;
-- 
2.17.1

Jason Wang

2018-Dec-12 10:08 UTC

head link

[PATCH net V2 4/4] vhost: log dirty page correctly

Vhost dirty page logging API is designed to sync through GPA. But we
try to log GIOVA when device IOTLB is enabled. This is wrong and may
lead to missing data after migration.

To solve this issue, when logging with device IOTLB enabled, we will:

1) reuse the device IOTLB translation result of GIOVA->HVA mapping to
   get HVA, for writable descriptor, get HVA through iovec. For used
   ring update, translate its GIOVA to HVA
2) traverse the GPA->HVA mapping to get the possible GPA and log
   through GPA. Pay attention this reverse mapping is not guaranteed
   to be unique, so we should log each possible GPA in this case.

This fix the failure of scp to guest during migration. In -next, we
will probably support passing GIOVA->GPA instead of GIOVA->HVA.

Fixes: 6b1e6cc7855b ("vhost: new device IOTLB API")
Reported-by: Jintack Lim <jintack at cs.columbia.edu>
Cc: Jintack Lim <jintack at cs.columbia.edu>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/net.c   |  3 +-
 drivers/vhost/vhost.c | 79 +++++++++++++++++++++++++++++++++++--------
 drivers/vhost/vhost.h |  3 +-
 3 files changed, 69 insertions(+), 16 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index ad7a6f475a44..784df2b49628 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1192,7 +1192,8 @@ static void handle_rx(struct vhost_net *net)
 		if (nvq->done_idx > VHOST_NET_BATCH)
 			vhost_net_signal_used(nvq);
 		if (unlikely(vq_log))
-			vhost_log_write(vq, vq_log, log, vhost_len);
+			vhost_log_write(vq, vq_log, log, vhost_len,
+					vq->iov, in);
 		total_len += vhost_len;
 		if (unlikely(vhost_exceeds_weight(++recv_pkts, total_len))) {
 			vhost_poll_queue(&vq->poll);
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 55e5aa662ad5..3660310604fd 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1733,11 +1733,67 @@ static int log_write(void __user *log_base,
 	return r;
 }
 
+static int log_write_hva(struct vhost_virtqueue *vq, u64 hva, u64 len)
+{
+	struct vhost_umem *umem = vq->umem;
+	struct vhost_umem_node *u;
+	u64 gpa;
+	int r;
+	bool hit = false;
+
+	list_for_each_entry(u, &umem->umem_list, link) {
+		if (u->userspace_addr < hva &&
+		    u->userspace_addr + u->size >+		    hva + len) {
+			gpa = u->start + hva - u->userspace_addr;
+			r = log_write(vq->log_base, gpa, len);
+			if (r < 0)
+				return r;
+			hit = true;
+		}
+	}
+
+	/* No reverse mapping, should be a bug */
+	WARN_ON(!hit);
+	return 0;
+}
+
+static void log_used(struct vhost_virtqueue *vq, u64 used_offset, u64 len)
+{
+	struct iovec iov[64];
+	int i, ret;
+
+	if (!vq->iotlb) {
+		log_write(vq->log_base, vq->log_addr + used_offset, len);
+		return;
+	}
+
+	ret = translate_desc(vq, (u64)(uintptr_t)vq->used + used_offset,
+			     len, iov, 64, VHOST_ACCESS_WO);
+	WARN_ON(ret < 0);
+
+	for (i = 0; i < ret; i++) {
+		ret = log_write_hva(vq,	(u64)(uintptr_t)iov[i].iov_base,
+				    iov[i].iov_len);
+		WARN_ON(ret);
+	}
+}
+
 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
-		    unsigned int log_num, u64 len)
+		    unsigned int log_num, u64 len, struct iovec *iov, int count)
 {
 	int i, r;
 
+	if (vq->iotlb) {
+		for (i = 0; i < count; i++) {
+			r = log_write_hva(vq, (u64)(uintptr_t)iov[i].iov_base,
+					  iov[i].iov_len);
+			if (r < 0)
+				return r;
+		}
+		return 0;
+	}
+
 	/* Make sure data written is seen before log. */
 	smp_wmb();
 	for (i = 0; i < log_num; ++i) {
@@ -1769,9 +1825,8 @@ static int vhost_update_used_flags(struct vhost_virtqueue
*vq)
 		smp_wmb();
 		/* Log used flag write. */
 		used = &vq->used->flags;
-		log_write(vq->log_base, vq->log_addr +
-			  (used - (void __user *)vq->used),
-			  sizeof vq->used->flags);
+		log_used(vq, (used - (void __user *)vq->used),
+			 sizeof vq->used->flags);
 		if (vq->log_ctx)
 			eventfd_signal(vq->log_ctx, 1);
 	}
@@ -1789,9 +1844,8 @@ static int vhost_update_avail_event(struct vhost_virtqueue
*vq, u16 avail_event)
 		smp_wmb();
 		/* Log avail event write */
 		used = vhost_avail_event(vq);
-		log_write(vq->log_base, vq->log_addr +
-			  (used - (void __user *)vq->used),
-			  sizeof *vhost_avail_event(vq));
+		log_used(vq, (used - (void __user *)vq->used),
+			 sizeof *vhost_avail_event(vq));
 		if (vq->log_ctx)
 			eventfd_signal(vq->log_ctx, 1);
 	}
@@ -2191,10 +2245,8 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
 		/* Make sure data is seen before log. */
 		smp_wmb();
 		/* Log used ring entry write. */
-		log_write(vq->log_base,
-			  vq->log_addr +
-			   ((void __user *)used - (void __user *)vq->used),
-			  count * sizeof *used);
+		log_used(vq, ((void __user *)used - (void __user *)vq->used),
+			 count * sizeof *used);
 	}
 	old = vq->last_used_idx;
 	new = (vq->last_used_idx += count);
@@ -2236,9 +2288,8 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct
vring_used_elem *heads,
 		/* Make sure used idx is seen before log. */
 		smp_wmb();
 		/* Log used index update. */
-		log_write(vq->log_base,
-			  vq->log_addr + offsetof(struct vring_used, idx),
-			  sizeof vq->used->idx);
+		log_used(vq, offsetof(struct vring_used, idx),
+			 sizeof vq->used->idx);
 		if (vq->log_ctx)
 			eventfd_signal(vq->log_ctx, 1);
 	}
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 466ef7542291..1b675dad5e05 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -205,7 +205,8 @@ bool vhost_vq_avail_empty(struct vhost_dev *, struct
vhost_virtqueue *);
 bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *);
 
 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
-		    unsigned int log_num, u64 len);
+		    unsigned int log_num, u64 len,
+		    struct iovec *iov, int count);
 int vq_iotlb_prefetch(struct vhost_virtqueue *vq);
 
 struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int type);
-- 
2.17.1

Michael S. Tsirkin

2018-Dec-12 14:20 UTC

head link

[PATCH net V2 2/4] vhost_net: switch to use mutex_trylock() in vhost_net_busy_poll()

On Wed, Dec 12, 2018 at 06:08:17PM +0800, Jason Wang
wrote:> We used to hold the mutex of paired virtqueue in
> vhost_net_busy_poll(). But this will results an inconsistent lock
> order which may cause deadlock if we try to bring back the protection
> of device IOTLB with vq mutex that requires to hold mutex of all
> virtqueues at the same time.
> 
> Fix this simply by switching to use mutex_trylock(), when fail just
> skip the busy polling. This can happen when device IOTLB is under
> updating which should be rare.
> 
> Fixes: commit 78139c94dc8c ("net: vhost: lock the vqs one by
one")
> Cc: Tonghao Zhang <xiangxia.m.yue at gmail.com>
> Signed-off-by: Jason Wang <jasowang at redhat.com>
Acked-by: Michael S. Tsirkin <mst at redhat.com>

and I think we should try to put this fix in 4.20 too.

> ---
>  drivers/vhost/net.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index ab11b2bee273..ad7a6f475a44 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -513,7 +513,13 @@ static void vhost_net_busy_poll(struct vhost_net *net,
>  	struct socket *sock;
>  	struct vhost_virtqueue *vq = poll_rx ? tvq : rvq;
>  
> -	mutex_lock_nested(&vq->mutex, poll_rx ? VHOST_NET_VQ_TX:
VHOST_NET_VQ_RX);
> +	/* Try to hold the vq mutex of the paired virtqueue. We can't
> +	 * use mutex_lock() here since we could not guarantee a
> +	 * consistenet lock ordering.
> +	 */
> +	if (!mutex_trylock(&vq->mutex))
> +		return;
> +
>  	vhost_disable_notify(&net->dev, vq);
>  	sock = rvq->private_data;
>  
> -- 
> 2.17.1

Michael S. Tsirkin

2018-Dec-12 14:24 UTC

head link

[PATCH net V2 3/4] Revert "net: vhost: lock the vqs one by one"

On Wed, Dec 12, 2018 at 06:08:18PM +0800, Jason Wang
wrote:> This reverts commit 78139c94dc8c96a478e67dab3bee84dc6eccb5fd. We don't
> protect device IOTLB with vq mutex, which will lead e.g use after free
> for device IOTLB entries. And since we've switched to use
> mutex_trylock() in previous patch, it's safe to revert it without
> having deadlock.
> 
> Fixes: commit 78139c94dc8c ("net: vhost: lock the vqs one by
one")
> Cc: Tonghao Zhang <xiangxia.m.yue at gmail.com>
> Signed-off-by: Jason Wang <jasowang at redhat.com>

Acked-by: Michael S. Tsirkin <mst at redhat.com>

I'd try to put this in 4.20 if we can
and it's needed for -stable I think.

Also looks like we should allow iotlb entries per vq
to improve locking. What do you think?
> ---
>  drivers/vhost/vhost.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 5915f240275a..55e5aa662ad5 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -295,11 +295,8 @@ static void vhost_vq_meta_reset(struct vhost_dev *d)
>  {
>  	int i;
>  
> -	for (i = 0; i < d->nvqs; ++i) {
> -		mutex_lock(&d->vqs[i]->mutex);
> +	for (i = 0; i < d->nvqs; ++i)
>  		__vhost_vq_meta_reset(d->vqs[i]);
> -		mutex_unlock(&d->vqs[i]->mutex);
> -	}
>  }
>  
>  static void vhost_vq_reset(struct vhost_dev *dev,
> @@ -895,6 +892,20 @@ static inline void __user *__vhost_get_user(struct
vhost_virtqueue *vq,
>  #define vhost_get_used(vq, x, ptr) \
>  	vhost_get_user(vq, x, ptr, VHOST_ADDR_USED)
>  
> +static void vhost_dev_lock_vqs(struct vhost_dev *d)
> +{
> +	int i = 0;
> +	for (i = 0; i < d->nvqs; ++i)
> +		mutex_lock_nested(&d->vqs[i]->mutex, i);
> +}
> +
> +static void vhost_dev_unlock_vqs(struct vhost_dev *d)
> +{
> +	int i = 0;
> +	for (i = 0; i < d->nvqs; ++i)
> +		mutex_unlock(&d->vqs[i]->mutex);
> +}
> +
>  static int vhost_new_umem_range(struct vhost_umem *umem,
>  				u64 start, u64 size, u64 end,
>  				u64 userspace_addr, int perm)
> @@ -976,6 +987,7 @@ static int vhost_process_iotlb_msg(struct vhost_dev
*dev,
>  	int ret = 0;
>  
>  	mutex_lock(&dev->mutex);
> +	vhost_dev_lock_vqs(dev);
>  	switch (msg->type) {
>  	case VHOST_IOTLB_UPDATE:
>  		if (!dev->iotlb) {
> @@ -1009,6 +1021,7 @@ static int vhost_process_iotlb_msg(struct vhost_dev
*dev,
>  		break;
>  	}
>  
> +	vhost_dev_unlock_vqs(dev);
>  	mutex_unlock(&dev->mutex);
>  
>  	return ret;
> -- 
> 2.17.1

Michael S. Tsirkin

2018-Dec-12 14:32 UTC

head link

[PATCH net V2 4/4] vhost: log dirty page correctly

On Wed, Dec 12, 2018 at 06:08:19PM +0800, Jason Wang
wrote:> Vhost dirty page logging API is designed to sync through GPA. But we
> try to log GIOVA when device IOTLB is enabled. This is wrong and may
> lead to missing data after migration.
> 
> To solve this issue, when logging with device IOTLB enabled, we will:
> 
> 1) reuse the device IOTLB translation result of GIOVA->HVA mapping to
>    get HVA, for writable descriptor, get HVA through iovec. For used
>    ring update, translate its GIOVA to HVA
> 2) traverse the GPA->HVA mapping to get the possible GPA and log
>    through GPA. Pay attention this reverse mapping is not guaranteed
>    to be unique, so we should log each possible GPA in this case.
> 
> This fix the failure of scp to guest during migration. In -next, we
> will probably support passing GIOVA->GPA instead of GIOVA->HVA.
> 
> Fixes: 6b1e6cc7855b ("vhost: new device IOTLB API")
> Reported-by: Jintack Lim <jintack at cs.columbia.edu>
> Cc: Jintack Lim <jintack at cs.columbia.edu>
> Signed-off-by: Jason Wang <jasowang at redhat.com>
It's a nasty bug for sure but it's been like this for a long
time so I'm inclined to say let's put it in 4.21,
and queue for stable.

So please split this out from this series.

Also, I'd like to see a feature bit that allows GPA in IOTLBs.
> ---
>  drivers/vhost/net.c   |  3 +-
>  drivers/vhost/vhost.c | 79 +++++++++++++++++++++++++++++++++++--------
>  drivers/vhost/vhost.h |  3 +-
>  3 files changed, 69 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index ad7a6f475a44..784df2b49628 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -1192,7 +1192,8 @@ static void handle_rx(struct vhost_net *net)
>  		if (nvq->done_idx > VHOST_NET_BATCH)
>  			vhost_net_signal_used(nvq);
>  		if (unlikely(vq_log))
> -			vhost_log_write(vq, vq_log, log, vhost_len);
> +			vhost_log_write(vq, vq_log, log, vhost_len,
> +					vq->iov, in);
>  		total_len += vhost_len;
>  		if (unlikely(vhost_exceeds_weight(++recv_pkts, total_len))) {
>  			vhost_poll_queue(&vq->poll);
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 55e5aa662ad5..3660310604fd 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -1733,11 +1733,67 @@ static int log_write(void __user *log_base,
>  	return r;
>  }
>  
> +static int log_write_hva(struct vhost_virtqueue *vq, u64 hva, u64 len)
> +{
> +	struct vhost_umem *umem = vq->umem;
> +	struct vhost_umem_node *u;
> +	u64 gpa;
> +	int r;
> +	bool hit = false;
> +
> +	list_for_each_entry(u, &umem->umem_list, link) {
> +		if (u->userspace_addr < hva &&
> +		    u->userspace_addr + u->size >> +		    hva + len) {
> +			gpa = u->start + hva - u->userspace_addr;
> +			r = log_write(vq->log_base, gpa, len);
> +			if (r < 0)
> +				return r;
> +			hit = true;
> +		}
> +	}
> +
> +	/* No reverse mapping, should be a bug */
> +	WARN_ON(!hit);
Maybe it should but userspace can trigger this easily I think.
We need to stop the device not warn in kernel log.

Also there's an error fd: VHOST_SET_VRING_ERR, need to wake it up.

> +	return 0;
> +}
> +
> +static void log_used(struct vhost_virtqueue *vq, u64 used_offset, u64 len)
> +{
> +	struct iovec iov[64];
> +	int i, ret;
> +
> +	if (!vq->iotlb) {
> +		log_write(vq->log_base, vq->log_addr + used_offset, len);
> +		return;
> +	}
This change seems questionable. used ring writes 
use their own machinery it does not go through iotlb.
Same should apply to log I think.
> +
> +	ret = translate_desc(vq, (u64)(uintptr_t)vq->used + used_offset,
> +			     len, iov, 64, VHOST_ACCESS_WO);
> +	WARN_ON(ret < 0);

Same thing here. translation failures can be triggered from guest.
warn on is not a good error handling strategy ...
> +
> +	for (i = 0; i < ret; i++) {
> +		ret = log_write_hva(vq,	(u64)(uintptr_t)iov[i].iov_base,
> +				    iov[i].iov_len);
> +		WARN_ON(ret);
> +	}
> +}
> +
>  int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
> -		    unsigned int log_num, u64 len)
> +		    unsigned int log_num, u64 len, struct iovec *iov, int count)
>  {
>  	int i, r;
>  
> +	if (vq->iotlb) {
> +		for (i = 0; i < count; i++) {
> +			r = log_write_hva(vq, (u64)(uintptr_t)iov[i].iov_base,
> +					  iov[i].iov_len);
> +			if (r < 0)
> +				return r;
> +		}
> +		return 0;
> +	}
> +
>  	/* Make sure data written is seen before log. */
>  	smp_wmb();
>  	for (i = 0; i < log_num; ++i) {
> @@ -1769,9 +1825,8 @@ static int vhost_update_used_flags(struct
vhost_virtqueue *vq)
>  		smp_wmb();
>  		/* Log used flag write. */
>  		used = &vq->used->flags;
> -		log_write(vq->log_base, vq->log_addr +
> -			  (used - (void __user *)vq->used),
> -			  sizeof vq->used->flags);
> +		log_used(vq, (used - (void __user *)vq->used),
> +			 sizeof vq->used->flags);
>  		if (vq->log_ctx)
>  			eventfd_signal(vq->log_ctx, 1);
>  	}
> @@ -1789,9 +1844,8 @@ static int vhost_update_avail_event(struct
vhost_virtqueue *vq, u16 avail_event)
>  		smp_wmb();
>  		/* Log avail event write */
>  		used = vhost_avail_event(vq);
> -		log_write(vq->log_base, vq->log_addr +
> -			  (used - (void __user *)vq->used),
> -			  sizeof *vhost_avail_event(vq));
> +		log_used(vq, (used - (void __user *)vq->used),
> +			 sizeof *vhost_avail_event(vq));
>  		if (vq->log_ctx)
>  			eventfd_signal(vq->log_ctx, 1);
>  	}
> @@ -2191,10 +2245,8 @@ static int __vhost_add_used_n(struct vhost_virtqueue
*vq,
>  		/* Make sure data is seen before log. */
>  		smp_wmb();
>  		/* Log used ring entry write. */
> -		log_write(vq->log_base,
> -			  vq->log_addr +
> -			   ((void __user *)used - (void __user *)vq->used),
> -			  count * sizeof *used);
> +		log_used(vq, ((void __user *)used - (void __user *)vq->used),
> +			 count * sizeof *used);
>  	}
>  	old = vq->last_used_idx;
>  	new = (vq->last_used_idx += count);
> @@ -2236,9 +2288,8 @@ int vhost_add_used_n(struct vhost_virtqueue *vq,
struct vring_used_elem *heads,
>  		/* Make sure used idx is seen before log. */
>  		smp_wmb();
>  		/* Log used index update. */
> -		log_write(vq->log_base,
> -			  vq->log_addr + offsetof(struct vring_used, idx),
> -			  sizeof vq->used->idx);
> +		log_used(vq, offsetof(struct vring_used, idx),
> +			 sizeof vq->used->idx);
>  		if (vq->log_ctx)
>  			eventfd_signal(vq->log_ctx, 1);
>  	}
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 466ef7542291..1b675dad5e05 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -205,7 +205,8 @@ bool vhost_vq_avail_empty(struct vhost_dev *, struct
vhost_virtqueue *);
>  bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *);
>  
>  int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
> -		    unsigned int log_num, u64 len);
> +		    unsigned int log_num, u64 len,
> +		    struct iovec *iov, int count);
>  int vq_iotlb_prefetch(struct vhost_virtqueue *vq);
>  
>  struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int
type);
> -- 
> 2.17.1

Michael S. Tsirkin

2018-Dec-12 14:33 UTC

head link

[PATCH net V2 1/4] vhost: make sure used idx is seen before log in vhost_add_used_n()

On Wed, Dec 12, 2018 at 06:08:16PM +0800, Jason Wang
wrote:> We miss a write barrier that guarantees used idx is updated and seen
> before log. This will let userspace sync and copy used ring before
> used idx is update. Fix this by adding a barrier before log_write().
> 
> Fixes: 8dd014adfea6f ("vhost-net: mergeable buffers support")
> Signed-off-by: Jason Wang <jasowang at redhat.com>

Acked-by: Michael S. Tsirkin <mst at redhat.com>

also for 4.20 and seems like a stable candidate.
> ---
>  drivers/vhost/vhost.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 6b98d8e3a5bf..5915f240275a 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -2220,6 +2220,8 @@ int vhost_add_used_n(struct vhost_virtqueue *vq,
struct vring_used_elem *heads,
>  		return -EFAULT;
>  	}
>  	if (unlikely(vq->log_used)) {
> +		/* Make sure used idx is seen before log. */
> +		smp_wmb();
>  		/* Log used index update. */
>  		log_write(vq->log_base,
>  			  vq->log_addr + offsetof(struct vring_used, idx),
> -- 
> 2.17.1

David Miller

2018-Dec-12 23:31 UTC

head link

[PATCH net V2 0/4] Fix various issue of vhost

From: Jason Wang <jasowang at redhat.com>
Date: Wed, 12 Dec 2018 18:08:15 +0800
> This series tries to fix various issues of vhost:
> 
> - Patch 1 adds a missing write barrier between used idx updating and
>   logging.
> - Patch 2-3 brings back the protection of device IOTLB through vq
>   mutex, this fixes possible use after free in device IOTLB entries.
> - Patch 4-7 fixes the diry page logging when device IOTLB is
>   enabled. We should done through GPA instead of GIOVA, this was done
>   through intorudce HVA->GPA reverse mapping and convert HVA to GPA
>   during logging dirty pages.
> 
> Please consider them for -stable.
> 
> Thanks
> 
> Changes from V1:
> - silent compiler warning for 32bit.
> - use mutex_trylock() on slowpath instead of mutex_lock() even on fast
>   path.
Hello Jason.

Look like Michael wants you to split out patch #4 and target
net-next with it.

So please do that and respin the first 3 patches here with Michael's
ACKs.

Thanks.

Jason Wang

2018-Dec-13 02:42 UTC

head link

[PATCH net V2 0/4] Fix various issue of vhost

On 2018/12/13 ??7:31, David Miller wrote:> From: Jason Wang <jasowang at redhat.com>
> Date: Wed, 12 Dec 2018 18:08:15 +0800
>
>> This series tries to fix various issues of vhost:
>>
>> - Patch 1 adds a missing write barrier between used idx updating and
>>    logging.
>> - Patch 2-3 brings back the protection of device IOTLB through vq
>>    mutex, this fixes possible use after free in device IOTLB entries.
>> - Patch 4-7 fixes the diry page logging when device IOTLB is
>>    enabled. We should done through GPA instead of GIOVA, this was done
>>    through intorudce HVA->GPA reverse mapping and convert HVA to GPA
>>    during logging dirty pages.
>>
>> Please consider them for -stable.
>>
>> Thanks
>>
>> Changes from V1:
>> - silent compiler warning for 32bit.
>> - use mutex_trylock() on slowpath instead of mutex_lock() even on fast
>>    path.
> Hello Jason.
>
> Look like Michael wants you to split out patch #4 and target
> net-next with it.
>
> So please do that and respin the first 3 patches here with Michael's
> ACKs.
>
> Thanks.

Yes, will send V3.

Thanks

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