From 841df922417eb82c835e93d4b93eb6a68c99d599 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Thu, 13 Dec 2018 10:53:37 +0800 Subject: 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") Acked-by: Michael S. Tsirkin Signed-off-by: Jason Wang Signed-off-by: David S. Miller --- drivers/vhost/vhost.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/vhost') 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), -- cgit From 476e8ba712fa6a479192dfc4301cd3765d9ba713 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Thu, 13 Dec 2018 10:53:38 +0800 Subject: 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 Acked-by: Michael S. Tsirkin Signed-off-by: Jason Wang Signed-off-by: David S. Miller --- drivers/vhost/net.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'drivers/vhost') 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; -- cgit From 86a07da34380bc9467fa407dc3e484488a8ad40d Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Thu, 13 Dec 2018 10:53:39 +0800 Subject: 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 Acked-by: Michael S. Tsirkin Signed-off-by: Jason Wang Signed-off-by: David S. Miller --- drivers/vhost/vhost.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) (limited to 'drivers/vhost') 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; -- cgit