diff options
| author | Michal Luczaj <mhal@rbox.co> | 2026-01-13 16:08:18 +0100 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-01-15 19:44:44 -0800 |
| commit | 0386bd321d0f95d041a7b3d7b07643411b044a96 (patch) | |
| tree | e33a102a90bf3335f45fe00ddbb3877589d5b010 /net | |
| parent | c4efd7a770c54964bf2d8c98b2f4fd10be13dc54 (diff) | |
vsock/virtio: Coalesce only linear skb
vsock/virtio common tries to coalesce buffers in rx queue: if a linear skb
(with a spare tail room) is followed by a small skb (length limited by
GOOD_COPY_LEN = 128), an attempt is made to join them.
Since the introduction of MSG_ZEROCOPY support, assumption that a small skb
will always be linear is incorrect. In the zerocopy case, data is lost and
the linear skb is appended with uninitialized kernel memory.
Of all 3 supported virtio-based transports, only loopback-transport is
affected. G2H virtio-transport rx queue operates on explicitly linear skbs;
see virtio_vsock_alloc_linear_skb() in virtio_vsock_rx_fill(). H2G
vhost-transport may allocate non-linear skbs, but only for sizes that are
not considered for coalescence; see PAGE_ALLOC_COSTLY_ORDER in
virtio_vsock_alloc_skb().
Ensure only linear skbs are coalesced. Note that skb_tailroom(last_skb) > 0
guarantees last_skb is linear.
Fixes: 581512a6dc93 ("vsock/virtio: MSG_ZEROCOPY flag support")
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://patch.msgid.link/20260113-vsock-recv-coalescence-v2-1-552b17837cf4@rbox.co
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/vmw_vsock/virtio_transport_common.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c index dcc8a1d5851e..26b979ad71f0 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c @@ -1359,9 +1359,11 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk, /* Try to copy small packets into the buffer of last packet queued, * to avoid wasting memory queueing the entire buffer with a small - * payload. + * payload. Skip non-linear (e.g. zerocopy) skbs; these carry payload + * in skb_shinfo. */ - if (len <= GOOD_COPY_LEN && !skb_queue_empty(&vvs->rx_queue)) { + if (len <= GOOD_COPY_LEN && !skb_queue_empty(&vvs->rx_queue) && + !skb_is_nonlinear(skb)) { struct virtio_vsock_hdr *last_hdr; struct sk_buff *last_skb; |