@@ -226,15 +226,14 @@ static int ipheth_rcvbulk_callback_ncm(struct urb *urb)
ncmh = urb->transfer_buffer;
if (ncmh->dwSignature != cpu_to_le32(USB_CDC_NCM_NTH16_SIGN) ||
- le16_to_cpu(ncmh->wNdpIndex) >= urb->actual_length) {
+ /* On iOS, NDP16 directly follows NTH16 */
+ ncmh->wNdpIndex != cpu_to_le16(sizeof(struct usb_cdc_ncm_nth16))) {
dev->net->stats.rx_errors++;
return retval;
}
- ncm0 = urb->transfer_buffer + le16_to_cpu(ncmh->wNdpIndex);
- if (ncm0->dwSignature != cpu_to_le32(USB_CDC_NCM_NDP16_NOCRC_SIGN) ||
- le16_to_cpu(ncmh->wHeaderLength) + le16_to_cpu(ncm0->wLength) >=
- urb->actual_length) {
+ ncm0 = urb->transfer_buffer + sizeof(struct usb_cdc_ncm_nth16);
+ if (ncm0->dwSignature != cpu_to_le32(USB_CDC_NCM_NDP16_NOCRC_SIGN)) {
dev->net->stats.rx_errors++;
return retval;
}
Original code allowed for the start of NDP16 to be anywhere within the URB based on the `wNdpIndex` value in NTH16. Only the start position of NDP16 was checked, so it was possible for even the fixed-length part of NDP16 to extend past the end of URB, leading to an out-of-bounds read. On iOS devices, the NDP16 header always directly follows NTH16. Rely on and check for this specific format. This, along with NCM-specific minimal URB length check that already exists, will ensure that the fixed-length part of NDP16 plus a set amount of DPEs fit within the URB. Note that this commit alone does not fully address the OoB read. The limit on the amount of DPEs needs to be enforced separately. Fixes: a2d274c62e44 ("usbnet: ipheth: add CDC NCM support") Cc: stable@vger.kernel.org Signed-off-by: Foster Snowhill <forst@pen.gy> Reviewed-by: Jakub Kicinski <kuba@kernel.org> --- v5: No code changes. Added Cc to stable and Reviewed-by Jakub tags. v4: https://lore.kernel.org/netdev/20250105010121.12546-5-forst@pen.gy/ Additionally check that ncmh->wNdpIndex points immediately after NTH16. This covers an unexpected on real devices, and highly unlikely otherwise, case where the bytes after NTH16 are set to `USB_CDC_NCM_NDP16_NOCRC_SIGN`, yet aren't the beginning of the NDP16 header. v3: https://lore.kernel.org/netdev/20241123235432.821220-4-forst@pen.gy/ Split out from a monolithic patch in v2 as an atomic change. v2: https://lore.kernel.org/netdev/20240912211817.1707844-1-forst@pen.gy/ No code changes. Update commit message to further clarify that `ipheth` is not and does not aim to be a complete or spec-compliant CDC NCM implementation. v1: https://lore.kernel.org/netdev/20240907230108.978355-1-forst@pen.gy/ --- drivers/net/usb/ipheth.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)