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authorColin Xu <colin.xu@intel.com>2021-02-02 03:19:23 +0300
committerMichael S. Tsirkin <mst@redhat.com>2021-02-23 15:52:59 +0300
commita6829c350ec6bec47752826c9738122308e1588c (patch)
tree03a3e48d1f56bc97ea4fed156d17841537a66f6a /drivers/virtio/virtio_input.c
parentd1e9aa9c34a776d43de819d3d334833aff5cca5a (diff)
downloadlinux-a6829c350ec6bec47752826c9738122308e1588c.tar.xz
virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm for MT.
In 'commit 29cc309d8bf1 ("HID: hid-multitouch: forward MSC_TIMESTAMP")', EV_MSC/MSC_TIMESTAMP is added to each before EV_SYN event. EV_MSC is configured as INPUT_PASS_TO_ALL. In case of a touch device which report MSC_TIMESTAMP: BE pass EV_MSC/MSC_TIMESTAMP to FE on receiving event from evdev. FE pass EV_MSC/MSC_TIMESTAMP back to BE. BE writes EV_MSC/MSC_TIMESTAMP to evdev due to INPUT_PASS_TO_ALL. BE receives extra EV_MSC/MSC_TIMESTAMP and pass to FE. >>> Each new frame becomes larger and larger. Disable EV_MSC/MSC_TIMESTAMP forwarding for MT. V2: Rebase. Signed-off-by: Colin Xu <colin.xu@intel.com> Link: https://lore.kernel.org/r/20210202001923.6227-1-colin.xu@intel.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Diffstat (limited to 'drivers/virtio/virtio_input.c')
-rw-r--r--drivers/virtio/virtio_input.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/drivers/virtio/virtio_input.c b/drivers/virtio/virtio_input.c
index f1f6208edcf5..244965c20d9b 100644
--- a/drivers/virtio/virtio_input.c
+++ b/drivers/virtio/virtio_input.c
@@ -64,6 +64,21 @@ static int virtinput_send_status(struct virtio_input *vi,
unsigned long flags;
int rc;
+ /*
+ * Since 29cc309d8bf1 (HID: hid-multitouch: forward MSC_TIMESTAMP),
+ * EV_MSC/MSC_TIMESTAMP is added to each before EV_SYN event.
+ * EV_MSC is configured as INPUT_PASS_TO_ALL.
+ * In case of touch device:
+ * BE pass EV_MSC/MSC_TIMESTAMP to FE on receiving event from evdev.
+ * FE pass EV_MSC/MSC_TIMESTAMP back to BE.
+ * BE writes EV_MSC/MSC_TIMESTAMP to evdev due to INPUT_PASS_TO_ALL.
+ * BE receives extra EV_MSC/MSC_TIMESTAMP and pass to FE.
+ * >>> Each new frame becomes larger and larger.
+ * Disable EV_MSC/MSC_TIMESTAMP forwarding for MT.
+ */
+ if (vi->idev->mt && type == EV_MSC && code == MSC_TIMESTAMP)
+ return 0;
+
stsbuf = kzalloc(sizeof(*stsbuf), GFP_ATOMIC);
if (!stsbuf)
return -ENOMEM;