[PATCH 6.19 153/220] net: usb: cdc_ncm: add ndpoffset to NDP32 nframes bounds check

Greg Kroah-Hartman
2026-03-23T13:57:19Z

From: Tobi Gaertner <tob.gaertner@me.com>

[ Upstream commit 77914255155e68a20aa41175edeecf8121dac391 ]

The same bounds-check bug fixed for NDP16 in the previous patch also
exists in cdc_ncm_rx_verify_ndp32(). The DPE array size is validated
against the total skb length without accounting for ndpoffset, allowing
out-of-bounds reads when the NDP32 is placed near the end of the NTB.

Add ndpoffset to the nframes bounds check and use struct_size_t() to
express the NDP-plus-DPE-array size more clearly.

Compile-tested only.

Fixes: 0fa81b304a79 ("cdc_ncm: Implement the 32-bit version of NCM Transfer Block")
Signed-off-by: Tobi Gaertner <tob.gaertner@me.com>
Link: https://patch.msgid.link/20260314054640.2895026-3-tob.gaertner@me.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/usb/cdc_ncm.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index a9d0162b5ee01..81d7e99fc0f09 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -1693,6 +1693,7 @@ int cdc_ncm_rx_verify_ndp32(struct sk_buff *skb_in, int ndpoffset)
struct usbnet *dev = netdev_priv(skb_in->dev);
struct usb_cdc_ncm_ndp32 *ndp32;
int ret = -EINVAL;
+ size_t ndp_len;

if ((ndpoffset + sizeof(struct usb_cdc_ncm_ndp32)) > skb_in->len) {
netif_dbg(dev, rx_err, dev->net, "invalid NDP offset <%u>\n",
@@ -1712,8 +1713,8 @@ int cdc_ncm_rx_verify_ndp32(struct sk_buff *skb_in, int ndpoffset)
sizeof(struct usb_cdc_ncm_dpe32));
ret--; /* we process NDP entries except for the last one */

- if ((sizeof(struct usb_cdc_ncm_ndp32) +
- ret * (sizeof(struct usb_cdc_ncm_dpe32))) > skb_in->len) {
+ ndp_len = struct_size_t(struct usb_cdc_ncm_ndp32, dpe32, ret);
+ if (ndpoffset + ndp_len > skb_in->len) {
netif_dbg(dev, rx_err, dev->net, "Invalid nframes = %d\n", ret);
ret = -EINVAL;
}
--
2.51.0