On Wed, Oct 02, 2024 at 04:02:06PM GMT, Stefano Garzarella wrote:
On Wed, Oct 02, 2024 at 09:41:42AM GMT, Michael S. Tsirkin wrote:
virtio_transport_send_pkt in now called on transport fast path,
under RCU read lock. In that case, we have a bug: virtio_add_sgs
is called with GFP_KERNEL, and might sleep.
Pass the gfp flags as an argument, and use GFP_ATOMIC on
the fast path.
Link: https://lore.kernel.org/all/hfcr2aget2zojmqpr4uhlzvnep4vgskblx5b6xf2ddosbsrke7@nt34bxgp7j2x
Fixes: efcd71af38be ("vsock/virtio: avoid queuing packets when intermediate queue is empty")
Reported-by: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Cc: Luigi Leonardi <luigi.leonardi@xxxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
Lightly tested. Christian, could you pls confirm this fixes the problem
for you? Stefano, it's a holiday here - could you pls help test!
Sure, thanks for the quick fix! I was thinking something similar ;-)
Thanks!
net/vmw_vsock/virtio_transport.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index f992f9a216f0..0cd965f24609 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -96,7 +96,7 @@ static u32 virtio_transport_get_local_cid(void)
/* Caller need to hold vsock->tx_lock on vq */
static int virtio_transport_send_skb(struct sk_buff *skb, struct virtqueue *vq,
- struct virtio_vsock *vsock)
+ struct virtio_vsock *vsock, gfp_t gfp)
{
int ret, in_sg = 0, out_sg = 0;
struct scatterlist **sgs;
@@ -140,7 +140,7 @@ static int virtio_transport_send_skb(struct sk_buff *skb, struct virtqueue *vq,
}
}
- ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
+ ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, gfp);
/* Usually this means that there is no more space available in
* the vq
*/
@@ -178,7 +178,7 @@ virtio_transport_send_pkt_work(struct work_struct *work)
reply = virtio_vsock_skb_reply(skb);
- ret = virtio_transport_send_skb(skb, vq, vsock);
+ ret = virtio_transport_send_skb(skb, vq, vsock, GFP_KERNEL);
if (ret < 0) {
virtio_vsock_skb_queue_head(&vsock->send_pkt_queue,
skb);
break;
@@ -221,7 +221,7 @@ static int virtio_transport_send_skb_fast_path(struct virtio_vsock *vsock, struc
if (unlikely(ret == 0))
return -EBUSY;
- ret = virtio_transport_send_skb(skb, vq, vsock);
nit: maybe we can add a comment here:
/* GFP_ATOMIC because we are in RCU section, so we can't sleep */
+ ret = virtio_transport_send_skb(skb, vq, vsock, GFP_ATOMIC);
if (ret == 0)
virtqueue_kick(vq);
--
MST
I'll run some tests and come back with R-b when it's done.
I replicated the issue enabling CONFIG_DEBUG_ATOMIC_SLEEP.
With that enabled, as soon as I run iperf-vsock, dmesg is flooded with
those messages. With this patch applied instead everything is fine.
I also ran the usual tests with various debugging options enabled and
everything seems okay.
With or without adding the comment I suggested in the previous email:
Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
