By definition, a DPE points at the start of a network frame/datagram.
Thus it makes no sense for it to point at anything that's part of the
NCM header. It is not a security issue, but merely an indication of
a malformed DPE.
Enforce that all DPEs point at the data portion of the URB, past the
NCM header.
Fixes: a2d274c62e44 ("usbnet: ipheth: add CDC NCM support")
Signed-off-by: Foster Snowhill <forst@xxxxxx>
---
v3:
Split out from a monolithic patch in v2 as an atomic change.
v2: https://lore.kernel.org/netdev/20240912211817.1707844-1-forst@xxxxxx/
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@xxxxxx/
---
drivers/net/usb/ipheth.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/net/usb/ipheth.c b/drivers/net/usb/ipheth.c
index 4b590a5269fd..48c79e69bb7b 100644
--- a/drivers/net/usb/ipheth.c
+++ b/drivers/net/usb/ipheth.c
@@ -253,7 +253,8 @@ static int ipheth_rcvbulk_callback_ncm(struct urb *urb)
dpe = ncm0->dpe16;
while (le16_to_cpu(dpe->wDatagramIndex) != 0 &&
le16_to_cpu(dpe->wDatagramLength) != 0) {
- if (le16_to_cpu(dpe->wDatagramIndex) >= urb->actual_length ||
+ if (le16_to_cpu(dpe->wDatagramIndex) < IPHETH_NCM_HEADER_SIZE ||
+ le16_to_cpu(dpe->wDatagramIndex) >= urb->actual_length ||
le16_to_cpu(dpe->wDatagramLength) > urb->actual_length -
le16_to_cpu(dpe->wDatagramIndex)) {
dev->net->stats.rx_length_errors++;
--
2.45.1
