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CDC-NCM: avoid overflow in sanity checking

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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 <oneukum@suse.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Oliver Neukum 2022-02-15 11:35:47 +01:00 committed by David S. Miller
parent 7e5b6a5c8c
commit 8d2b1a1ec9
1 changed files with 4 additions and 4 deletions
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8
drivers/net/usb/cdc_ncm.c
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@ -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 @@ next_ndp:
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",