[PATCH v3 2/2] net: usb: cdc_ncm: add ndpoffset to NDP32 nframes bounds check
From: tobgaertner <hidden>
Date: 2026-03-14 05:47:03
Also in:
linux-usb
Subsystem:
networking drivers, the rest, usb cdc ethernet driver, usb networking drivers · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Oliver Neukum
From: Tobi Gaertner <redacted>
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 <redacted>
---
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 a9d0162b5..81d7e99fc 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; }
--
2.43.0