From 49909c9f8458cacb5b241106cba65aba5a6d8f4c Mon Sep 17 00:00:00 2001 From: Oliver Neukum Date: Tue, 15 Feb 2022 11:35:47 +0100 Subject: [PATCH] CDC-NCM: avoid overflow in sanity checking commit 8d2b1a1ec9f559d30b724877da4ce592edc41fdc upstream. A broken device may give an extreme offset like 0xFFF0 and a reasonable length for a fragment. In the sanity check as formulated now, this will create an integer overflow, defeating the sanity check. Both offset and offset + len need to be checked in such a manner that no overflow can occur. And those quantities should be unsigned. Signed-off-by: Oliver Neukum Reviewed-by: Greg Kroah-Hartman Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/usb/cdc_ncm.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c index e303b522efb50..15f91d691bba3 100644 --- a/drivers/net/usb/cdc_ncm.c +++ b/drivers/net/usb/cdc_ncm.c @@ -1715,10 +1715,10 @@ int cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in) { struct sk_buff *skb; struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0]; - int len; + unsigned int len; int nframes; int x; - int offset; + unsigned int offset; union { struct usb_cdc_ncm_ndp16 *ndp16; struct usb_cdc_ncm_ndp32 *ndp32; @@ -1790,8 +1790,8 @@ int cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in) break; } - /* sanity checking */ - if (((offset + len) > skb_in->len) || + /* sanity checking - watch out for integer wrap*/ + if ((offset > skb_in->len) || (len > skb_in->len - offset) || (len > ctx->rx_max) || (len < ETH_HLEN)) { netif_dbg(dev, rx_err, dev->net, "invalid frame detected (ignored) offset[%u]=%u, length=%u, skb=%p\n",