netfilter: synproxy: fix BUG_ON triggered by corrupt TCP packets

TCP packets hitting the SYN proxy through the SYNPROXY target are not
validated by TCP conntrack. When th->doff is below 5, an underflow happens
when calculating the options length, causing skb_header_pointer() to
return NULL and triggering the BUG_ON().

Handle this case gracefully by checking for NULL instead of using BUG_ON().

Reported-by: Martin Topholm <[email protected]>
Tested-by: Martin Topholm <[email protected]>
Signed-off-by: Patrick McHardy <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

0 files changed, 0 insertions, 0 deletions