Re: possible integer overflow in CDC-NCM checks

Oliver Neukum [off-list ref] writes:

CDC-NCM: avoid overflow in sanity checking 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. It needs to be rewritten as a
subtraction and the variables should be unsigned. Signed-off-by: Oliver
Neukum [off-list ref] --- drivers/net/usb/cdc_ncm.c | 6 +++--- 1
file changed, 3 insertions(+), 3 deletions(-) diff --git
a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c index
e303b522efb5..f78fccbc4b93 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; @@ -1791,7 +1791,7 @@ int
cdc_ncm_rx_fixup(struct usbnet *dev, struct sk_buff *skb_in) } /* sanity
checking */ - if (((offset + len) > skb_in->len) || + if ((offset >
skb_in->len - len) || (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", -- 2.34.1

I don't mind taking a look at it, but that's beyond unreadable...

Could you please resend using "git send-email" or something else that
works?



Bjørn