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fix: don't expose eMMC as USB mass storage when no image is mounted #741

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fix: don't expose eMMC as USB mass storage when no image is mounted #741

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14 changes: 6 additions & 8 deletions kvmapp/system/init.d/S03usbdev
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Original file line number Diff line number Diff line change
Expand Up @@ -106,17 +106,15 @@ start_usb_dev(){
fi
echo "NanoKVM USB Mass Storage0520" > functions/mass_storage.disk0/lun.0/inquiry_string
disk=$(cat /boot/usb.disk0)
if [ -z "${disk}" ]
if [ -n "${disk}" ]
then
# if [ ! -e /mnt/usbdisk.img ]
# then
# fallocate -l 8G /mnt/usbdisk.img
# mkfs.vfat /mnt/usbdisk.img
# fi
echo /dev/mmcblk0p3 > functions/mass_storage.disk0/lun.0/file
else
cat /boot/usb.disk0 > functions/mass_storage.disk0/lun.0/file
fi
# When usb.disk0 is empty, no backing file is set. The device
# reports "no media" (removable=1). Previously this defaulted to
# /dev/mmcblk0p3, exposing the NanoKVM's raw eMMC partition as a
# USB disk — causing Legacy BIOS systems to hang during boot.
# See: https://github.com/sipeed/NanoKVM/issues/633
fi

ls /sys/class/udc/ | cat > UDC
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25 changes: 13 additions & 12 deletions server/service/storage/image.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,6 @@ import (

const (
imageDirectory = "/data"
imageNone = "/dev/mmcblk0p3"
cdromFlag = "/sys/kernel/config/usb_gadget/g0/functions/mass_storage.disk0/lun.0/cdrom"
mountDevice = "/sys/kernel/config/usb_gadget/g0/functions/mass_storage.disk0/lun.0/file"
inquiryString = "/sys/kernel/config/usb_gadget/g0/functions/mass_storage.disk0/lun.0/inquiry_string"
Expand Down Expand Up @@ -109,16 +108,17 @@ func (s *Service) MountImage(c *gin.Context) {
}

// mount
image := req.File
if image == "" {
image = imageNone
}

if err := os.WriteFile(mountDevice, []byte(image), 0o666); err != nil {
log.Errorf("mount file %s failed: %s", image, err)
rsp.ErrRsp(c, -2, "mount image failed")
return
if req.File != "" {
if err := os.WriteFile(mountDevice, []byte(req.File), 0o666); err != nil {
log.Errorf("mount file %s failed: %s", req.File, err)
rsp.ErrRsp(c, -2, "mount image failed")
return
}
}
// When req.File is empty the device stays unmounted (no media).
// Previously this wrote /dev/mmcblk0p3, exposing the NanoKVM's raw
// eMMC partition as a USB disk — causing Legacy BIOS boot hangs.
// See: https://github.com/sipeed/NanoKVM/issues/633

h := hid.GetHid()
h.Lock()
Expand Down Expand Up @@ -156,8 +156,9 @@ func (s *Service) GetMountedImage(c *gin.Context) {
return
}

image := strings.ReplaceAll(string(content), "\n", "")
if image == imageNone {
image := strings.TrimSpace(string(content))
if image == "/dev/mmcblk0p3" {
// Backward compat: treat eMMC partition as "no image mounted"
image = ""
}

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